Grid for a battery plate, method of producing the same, and battery using the same

ABSTRACT

The invention provides a grid for a battery plate in which, when a metal sheet is formed into a grid-like shape, rupture due to torsion or stress concentration does not occur in a basal portion of a wire which is drawn out from a node of the grid, thereby preventing corrosion due to electrolyte from advancing so as not to cause a crack of corrosion in an early stage. The invention provides also a battery using the grid for a battery plate, a method of producing the grid for a battery plate, and a battery using it.  
     In a grid for a battery plate in which large number of slits each configured by a cut elongating in a longitudinal direction are formed in a metal sheet in a zigzag pattern, the metal sheet is stretched in the width direction to develop the slits, and nodes are connected to one another to form a lattice-like shape, by four wires which are obliquely bent to be drawn out, at least one of the four wires connected to each of the nodes is bent in an oblique direction via a drawn-out portion which is drawn out from the node in a substantially longitudinal direction.  
     A small slope having an inclination angle, or a curved face is interposed between slopes of peripheral side faces in a range from a valley to a ridge in a disk cutter which is placed in a disk cutter roll for a rotary expander. An inclined face which more approaches the axis as being nearer to a disk face on the side where a groove is formed, in a range from a ridge to a valley where the groove is formed, in a disk cutter which is placed in a disk cutter roll for a rotary expander. A small slope is interposed between a valley and at least a front slope of a peripheral side face of a ridge which is rearward adjacent to the valley, the small slope having an inclination angle which is between angles of the two faces. A grid for a battery plate is produced by using disk cutters in which a range from a valley to a groove is chamfered. The production method is configured so that, in each of ridges of endmost disk cutters which are disposed respectively on both the ends of a lower disk cutter roll, a peripheral side face configured by a reference circumferential face of a predetermined radius is formed, and, in each of valleys serving as endmost node forming valleys in the endmost disk cutters, an inward inclined face is formed, the inward inclined face being a tapered face which is recessed toward the center from the reference circumferential face, and which is inward inclined.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a grid for a battery plate which is produced by a rotary expander, a method of producing it, and a battery using it.

[0002] A battery plate of a lead storage battery is configured by filling an active material into meshes of a grid made of lead or a lead alloy. Such a grid is often produced by directly forming a grid-like shape by means of, for example, casting of lead or a lead alloy, or alternatively by forming meshes in a metal sheet made of lead or a lead alloy (hereinafter, a sheet such as that containing lead, a lead alloy, or another alloy is referred to merely as a metal sheet) by an expander. The expander is of the reciprocal type in which meshes are sequentially formed in a metal sheet with starting from both the ends of the sheet, by vertical motions of a die cutter, or of the rotary type in which slits are formed in a zigzag pattern by rotation of a disk cutter, and the metal sheet is stretched from both the sides to develop the slits into meshes. As shown in FIG. 37, in a disk cutter 1 which is used in the rotary expander, large numbers of ridges 1 a and valleys 1 b are alternately formed at regular intervals along a circumferential direction on the peripheral side face of a metal disk. The valleys 1 b are curved faces consisting of the circumferential face itself constituting the peripheral side face of the disk of the disk cutter 1. The oval enlarged view in FIG. 37 shows the circumferential face in a form developed to a plane. Each of the ridges 1 a is formed by protruding the circumferential face of the disk cutter 1 in a ridge-like shape toward the outer periphery. The apex of the ridge is rounded and formed with being shifted toward the front side in the rotational direction (indicated by the arrow in the figure).

[0003] In the disk cutter 1, grooves 1 c are formed in both the disk-like faces and in every other valley 1 b. Each of the grooves 1 c is a groove which has a width that is equal to the length (the distance between adjacent ridges 1 a) of the corresponding valley 1 b, and a depth that is about one half of the thickness of the valley 1 b (the thickness of the disk cutter 1), and which is radially formed in the disk face of the disk cutter 1. The groove 1 c is formed so as to open in the valley 1 b in the outer peripheral side and have a length of some degree toward the center. The grooves 1 c which are formed in every other valley 1 b are arranged so as to be alternate on both the faces.

[0004] A large number of such disk cutters 1 are arranged on a common rotation shaft with being separated from each other by a distance which is approximately equal to the thickness of the disk cutters 1, thereby forming a disk cutter roll. As shown in FIG. 38, two disk cutter rolls each configured by a large number of such disk cutters 1 are vertically arranged, and a lead sheet 2 is passed between the rolls, thereby forming slits 2 a. In this case, as shown in FIG. 39(a), the upper and lower disk cutter rolls are placed respectively at levels which allow the valleys 1 b of the upper and lower disk cutter 1 to slightly overlap with each other. Furthermore, the upper and lower disk cutter rolls are placed with being shifted in the axial direction by a half pitch so that each of the disk cutters 1 of the lower disk cutter roll is positioned between the disk cutters 1 of the upper disk cutter roll. The rotational phase is adjusted so that, when the valley 1 b in which the groove 1 c is formed in one disk face of the upper disk cutter 1 reaches the lower end, the valley 1 b in which the groove 1 c is formed in the other disk face of the lower disk cutter 1 reaches the upper end, and, when the ridge 1 a of the upper disk cutter 1 reaches the lower end, as shown in FIG. 39(b), the ridge 1 a of the lower disk cutter 1 reaches the upper end.

[0005] When a metal sheet 2 is passed between the disk cutter rolls, as shown in FIG. 38, the slits 2 a are formed in the metal sheet 2 by the ridges 1 a of the upper and lower disk cutters 1, and thin wires 2 b between the slits 2 a which are formed adjacently in the width direction of the metal sheet 2 are pressed by the upper and lower ridges 1 a to alternately vertically protrude in a ridge-like shape. As shown in FIG. 39(a), in the valleys 1 b of the upper and lower disk cutters 1 where the grooves 1 c face each other in opposite directions, the metal sheet 2 is cut so that the slits 2 a are continuously formed, and, in the valleys where the grooves 1 c face each other, the metal sheet 2 is not cut so that the slits 2 a are intermitted to form nodes 2 c. In the metal sheet 2, therefore, the slits 2 a each having a length corresponding to two ride-like shapes which are formed by pressing of the ridges 1 a are continuously formed in the transportation direction while being intermitted in the nodes 2 c. Adjacent ones of the slits 2 a are similarly continuously formed while their nodes 2 c are shifted from each other by a half pitch. Therefore, the slits 2 a are formed in a zigzag pattern as shown in a plan view which is in a circle of FIG. 38.

[0006] The metal sheet (lead sheet) 2 in which the many slits 2 a are formed as described above is stretched toward both the sides in the width direction in a subsequent step. As a result, as shown in FIG. 40, the slits 2 a are widened so as to form meshes, whereby a lattice-like grid is formed in which the nodes 2 c are connected to one another by four wires 2 b that are obliquely bent to be drawn out.

[0007] As shown in FIG. 47, endmost disk cutters 4 are disposed on both the axial ends of the lower disk cutter roll, respectively. In each of the endmost disk cutters 4, as shown in FIGS. 48 and 49, ridges 4 a and valleys 4 b are alternately arranged in the peripheral edge. The valleys 4 b, and grooves 4 c which are formed in the valleys 4 b are configured in the strictly identical manner as the valleys 1 b and the grooves 1 c of the usual disk cutters 1. In each of the ridges 4 a, however, a peripheral side face configured by a reference circumferential face is formed. Namely, in the endmost disk cutters 4, the ridges 4 a do not protrude in a ridge-like shape toward the outer periphery, and the valleys 4 b do not have a shape which is relatively recessed with respect to the ridges 4 a. The endmost disk cutters 4 are placed at the ends of the lower disk cutter roll so as to be outward juxtaposed with the usual disk cutters 1 at the ends of the upper disk cutter roll, respectively.

[0008] In the ends of the disk cutter rolls, as shown in FIG. 47(b), the ridges 4 a of the endmost disk cutters 4 of the lower disk cutter roll overlap with the ridges 1 a of the end disk cutters 1 of the upper disk cutter roll, whereby the metal sheet 2 between the ridges are cut so that the slits 2 a are formed and the wires 2 b downward protrude in a ride-like shape. As shown in FIGS. 47(a) and 47(c), also in the adjacent portions (the right end in FIG. 47(a), and the left end in FIG. 47(b)) where the grooves 4 c of the valleys 4 b of the lower endmost disk cutters 4, and the grooves 1 c of the valleys 1 b of the upper end disk cutters 1 face each other in opposite directions, the valleys 1 b and 4 b slightly overlap with each other, whereby the metal sheet 2 is cut and the slits 2 a are continuously formed. However, in the adjacent portions (the left end in FIG. 47(a), and the right end in FIG. 47(b)) where the grooves 4 c of the valleys 4 b of the lower endmost disk cutters 4, and the grooves 1 c of the valleys 1 b of the upper end disk cutters 1 are formed in the opposed faces so as to face each other, the grooves 1 c and 4 c cause the peripheral side faces of the valleys 1 b and 4 b not to overlap with each other, and the metal sheet 2 is not cut. Therefore, endmost nodes 2 f which are similar to the nodes 2 c are formed. Since no slit 2 a is formed in the outer end, the endmost nodes 2 f are directly connected to frame portions 2 g which are formed in the ends in the width direction of the metal sheet 2.

[0009] The metal sheet 2 in which the many slits 2 a are formed as described above is stretched toward both the sides in the width direction in the subsequent step of the rotary expander. As a result, as shown in FIG. 50, the slits 2 a are widened so as to form meshes, whereby a lattice-like grid is formed in which the nodes 2 c and the endmost nodes 2 f are connected to one another by four wires 2 b that are obliquely drawn out. In practice, the nodes 2 c are pulled by the wires 2 b during the developing step to be inclined in a twisting direction. In FIG. 50, however, such twist is omitted and the grid is diagrammatically shown.

[0010] Problem (1) to be Solved by the Invention

[0011] In the conventional grid described above, when the slits 2 a are formed in the metal sheet 2, the wires 2 b connected to each of the nodes 2 c are pressed by the ridges 1 a to be bent in the basal end. During a process of developing the slits 2 a into a lattice-like shape, the tensile stress applied to the wires 2 b is concentrated in the basal end where the wires are connected to the node 2 a. When stress is concentrated in the basal end of the node 2 c, an excessive load is applied to the basal end during the developing process, and rupture may occur in the basal end. Therefore, corrosion due to electrolyte easily advances with starting from the basal end, thereby causing the possibility that a crack of corrosion occurs in the wires 2 b during use of a battery.

[0012] Consequently, a conventional grid which is produced by using a rotary expander has a problem in that a basal end where a wire is connected to a node is cracked by corrosion and the life of a battery is shortened.

[0013] Problem (2) to be Solved by the Invention

[0014] In the conventional disk cutter 1 configured as described above, as shown in FIG. 41, each of the ridges 1 a is not formed as a ridge having an isosceles triangular shape, but formed into a scalene triangular shape in which the apex 1 i is formed with being shifted toward the front side in the rotational direction. The rotating disk cutter 1 forms the slits 2 a in the metal sheet 2, and presses the fence-like portion between the slits 2 a by the ridges 1 a to project the portion in a ridge-like shape, thereby forming the wires 2 b. In the case where the ridges 1 a have an isosceles triangular shape, therefore, the front half of the fence-like portion between the slits 2 a protrudes in a ridge-like shape while being gradually stretched by the apexes 1 i of the ridges 1 a, and in contrast the latter half is pressed only by the rear slopes of the ridges 1 a which are in rear of the apexes of the ridges 1 a. In each of the wires 2 b between the slits 2 a and protruding in a ridge-like shape, consequently, the front half is more elongated to be thinned. When a grid is formed by stretching such wires, there arises a defect that walls of the meshes are uneven in thickness. By contrast, when the apex 1 i of each ridge 1 a is formed with being shifted toward the front side, the fence-like portion between the slits 2 a is first pressed by a substantially whole front area of the slope which is raised by a steep angle θ₁₀ of the front side, so as to protrude at a relatively early timing to form the wires 2 b. In accordance with the rotation, also the rear area gradually protrudes. As a result, the whole wires 2 b are uniformly extended and the thickness is even. Because of the above, conventionally, a rotary expander uses the disk cutter 1 in which the apex 1 i of the ridge 1 a is formed with being shifted toward the front side in the rotational direction (see Japanese Patent Publication (Kokoku) No. SH059-35694).

[0015] The metal sheet 2 in which the many slits 2 a are formed as described above is stretched toward both the sides in the width direction in a subsequent step, whereby the slits 2 a are widened to form rhombic meshes, with the result that a grid for a battery plate is formed.

[0016] With respect to the angles at which the slopes on both the sides of the apex 1 i of each ridge 1 a are connected to the valleys 1 b, the front angle θ₁₀ is steeper than the rear angle θ₂₀. As shown in FIG. 42, also in each of the wires 2 b which are formed as a result of protrusion of the fence-like portion between the slits 2 a of the metal sheet 2 in a ridge-like shape, therefore, the front bending angle θ₁₁ is steeper than the rear bending angle θ₂₁. When the metal sheet 2 is stretched to widen the slits 2 a to form meshes, therefore, the degree of cut into the nodes 2 c is large or the strength is reduced in the front end where the wires 2 b between the slits 2 a are sharply bent. As a result, as shown in FIG. 43, there arises the possibility that the length of the nodes 2 c is reduced, or rupture occurs in edge portions (edge portions D in FIG. 43). In FIG. 43, twisting is not shown, and the grid is schematically shown.

[0017] When a grid for a battery plate is produced by using the disk cutters 1 of a conventional rotary expander, particularly in the case where the grid is used as a positive plate, the nodes 2 c of the meshes and the edge portions D are corroded by electrolyte with starting from rupture or the like to cause a crack of corrosion, thereby producing a problem in that the capacity of a lead storage battery is reduced or the life of the battery is shortened.

[0018] Problem (3) to be Solved by the Invention

[0019] As shown in FIG. 44, the wires 2 b are pressed by the ridges 1 a of the disk cutters 1 to be elastically deformed in a ridge-like shape in which the apex 2 e is bent at the steepest curvature. Even when the ridges are stretched in an oblique direction in the developing step to become linear, therefore, the apex 2 e of each ridge remains to be elastically deformed and hence cannot be stretched into a fully linear form. When the wires 2 b are stretched in the developing step, consequently, the tensile stress in this process is easily concentrated in both sides of the elastically deformed portion of the apex 2 e which is bent.

[0020] In practice, the wires 2 b are developed in the developing step not only by being obliquely stretched to become linear, also by being twisted at the ends in opposite directions as indicated by the arrows D and E in FIG. 45. As shown in FIG. 39(a) or FIGS. 47(a) and 47(c), in each of the nodes 2 c, the sides in the width direction of the metal sheet 2 are vertically pressed in opposite directions by the valleys 1 b of the upper and lower the disk cutters 1. Therefore, a level difference which approximately corresponds to the thickness of the sheet is formed between one side in the width direction and the other side, and also positions where the wires 2 b are drawn out are different in level. As shown in FIG. 45, in a node 2 c which is connected to one end of a certain wire 2 b, one side in the width direction is higher in level, and the other side is lower. By contrast, in another node 2 c which is connected to the other end of the same wire 2 b, one side in the width direction is lower in level, and the other side is higher. When the metal sheet 2 is stretched in the width direction, therefore, the nodes 2 c are stretched toward both the sides in the width direction by the wires 2 b which are different in level, with the result that the nodes 2 c, 2 c which are shown in right upper, and left lower portions of FIG. 45 are twisted in the direction of the arrow F, and in contrast the nodes 2 c, 2 c which are shown in left upper, and right lower portions of FIG. 45 are twisted in the opposite direction or the direction of the arrow G. The wire 2 b between the right upper and left upper nodes 2 c, 2 c is developed while the ends are twisted in opposite directions or the directions of the arrows D and E, respectively. As a result, each of the wires 2 b is stretched while the ends are twisted in opposite directions, so that the torsion stress is easily concentrated in both sides of the elastically deformed portion of the apex 2 e.

[0021] In each of the wires 2 b, consequently, the tensile stress and the torsion stress in the developing step are concentrated on both the sides of the elastically deformed portion of the apex 2 e which remains to be bent, and a constricted part may be formed. Therefore, a grid which is produced by using a conventional rotary expander has a problem in that rupture often occurs in the portion. In the case where the metal sheet 2 is thick or has a thickness larger than 1.0 mm, or the case where the disk cutters 1 in which the ridges 1 a largely protrude are used, particularly, rupture often occurs in the vicinity of the apex 2 e of each wire 2 b. When a battery is produced by using such a grid as a battery plate, local corrosion occurs in the rupture portion, or in the worst case a crack of corrosion occurs the wires 2 b, thereby causing the life of the battery to be shortened. The invention has been conducted in order to cope with the above-discussed circumstances. It is an object of the invention to provide a grid for a battery plate in which an inclined face is formed on a peripheral side face of each ridge of a disk cutter, and wires are formed in a ridge-like shape in a state where the wires are pretwisted, thereby causing the wires to hardly rupture, and also a method of producing the grid.

[0022] Problem (4) to be Solved by the Invention

[0023] The shape of the disk cutter 1 and production steps in the production of a grid for a battery plate in which disk cutters for a rotary expander are used are shown in FIGS. 37 to 40. In a process of producing the grid for a battery plate, the slits 2 a and the nodes 2 c are formed in the metal sheet 2. As apparent from FIG. 46(a), the cutting is conducted while pressing each of the nodes 2 c against a ridgeline 1 k of the portion of the disk cutter 1 where the groove 1 c of the peripheral side face of the valley 1 b is formed. As shown in FIG. 46(b), therefore, stress is concentrated on the portion against which the ridgeline 1 k is pressed, and rupture sometimes occurs in the node 2 c. When such rupture once occurs, corrosion advances with starting from the rupture, and crack of corrosion finally occurs, thereby producing a problem in that the capacity of a lead storage battery is reduced or the life of the battery is shortened.

[0024] The invention has been conducted in order to cope with the above-discussed circumstances. It is an object of the invention to provide a method of producing a grid for a battery in which stress concentration is relaxed and rupture hardly occurs in the node 2 c, and a battery using the grid for a battery.

[0025] Problem (5) to be Solved by the Invention

[0026] In the formation of the nodes 2 c and the endmost nodes 2 f of the metal sheet 2, as shown in FIG. 47(a) and 47(c), the sides in the width direction are vertically pressed in opposite directions by the valleys 1 b and 4 b of the upper and lower disk cutters 1 and the endmost disk cutters 4 in which the grooves 1 c are opposed to each other. Therefore, the sides in the width direction are vertically deformed with respect to each other by a large degree corresponding to the thickness of the metal sheet 2 or more, and the metal sheet 2 of the endmost nodes 2 f is stretched to be thinned in accordance with the deformation. When the metal sheet 2 is stretched toward both the sides in the width direction, development is conducted while the wires 2 b drawn out from the nodes 2 c and the endmost nodes 2 f which are thinned by the vertical deformation are laterally pulled to be obliquely bent. Therefore, stress is concentrated on the nodes 2 c and the endmost nodes 2 f, and the possibilities that rupture occurs during a production process, and that, after a battery is produced by using such a grid for a battery, a crack of corrosion is caused between the nodes and the wires 2 b by corrosion or heat are increased. When a crack of corrosion of the wires 2 b occurs in one of the endmost nodes 2 f connected to the frame portions 2 g of the metal sheet 2 where a lug of the grid is formed for current collection from the battery plate, the plate portion that is on the other side in the width direction is connected to the lug through a detour. As a result, the current hardly flows, so that disadvantages such as that the active material in the portion is not effectively used, and that a large current flows through the detour to generate heat are largely increased. When a crack of corrosion occurs in any one of the nodes 2 c other than the endmost nodes 2 f, similarly, a current hardly flows from the plate portion that is on the other side in the width direction with respect to the node 2 c. However, influence due to the above is more extremely reduced as the node 2 c is more separated from the frame portions 2 g where a lug is formed.

SUMMARY OF THE INVENTION

[0027] The invention has been conducted in order to solve the above-discussed problems. It is an object of the invention to provide a grid for a battery plate in which various unique measures are taken mainly on the peripheral side faces of the valleys 1 b between the ridges 1 a of the disk cutters 1, to prevent rupture from occurring during a process of producing the grid, and corrosion and a crack of corrosion from occurring in nodes and edges of meshes of the grid for a battery plate, thereby preventing the capacity of a lead storage battery from being reduced, and the life of the battery from being shortened, a method of producing the grid, and a battery using the grid.

[0028] In the endmost nodes 2 f connected to the frame portions 2 g of the metal sheet 2, a crack of corrosion of the wires 2 b easily occurs in the same manner as in the other nodes 2 c. Consequently, there arises a problem in that, in many batteries, the capacity is largely reduced by a crack in the endmost nodes 2 f. The invention has been conducted in order to cope with the above-discussed circumstances. It is an object of the invention to provide a grid for a battery plate in which the peripheral side faces of the valleys of the endmost disk cutters are recessed toward the center, whereby deformation of endmost nodes is reduced so that a crack of wires hardly occurs, and a method of producing the grid.

[0029] Means for Solving Problem (1)

[0030] The invention set forth in claim 1 provides a grid for a battery plate in which a large number of slits each configured by a out elongating in a longitudinal direction are formed in a metal sheet in a zigzag pattern, the metal sheet is stretched in a width direction to develop the slits, and nodes configured between slits that are adjacent in the longitudinal direction are connected to one another to form a lattice-like shape, by four wires which are configured between slits that are adjacent in the width direction, and which are obliquely bent to be drawn out, wherein

[0031] at least one of the four wires connected to each of the nodes is bent in a predetermined oblique direction via a drawn-out portion which is drawn out from the node in a substantially longitudinal direction.

[0032] According to the invention set forth in claim 1, since at least one wire is bent at the tip end of the substantially straight drawn-out portion which is drawn out from the node, tensile stress produced during a process of developing the wire is applied with being dispersed not only to the basal end of the node but also to the whole drawn-out portion, and hence at least the wire can be prevented from being easily corroded.

[0033] The invention set forth in claim 2 provides a method of producing a grid for a battery plate in which a metal sheet is passed between two rotating disk cutter rolls in each of which a plurality of disk cutters are placed on a same shaft with forming a gap therebetween, each of the disk cutters being configured by: alternately forming ridges which protrude in a ridge-like shape toward an outer peripheral side, and valleys composed of a circumferential face or a flat face along a circumferential direction on a peripheral side face of a disk; and forming grooves which are opened in an outer peripheral end and in every other valley alternately formed in both faces of the disk, in peripheral edges of both the faces of the disk, the disk cutter rolls being opposed to each other in a manner that the ridges of the disk cutters of one of the disk cutter rolls are placed in the gaps of the disk cutters of another disk cutter roll, whereby slits each configured by a cut elongating in a longitudinal direction are formed in the metal sheet, wherein

[0034] the valleys of the disk cutters of one of the disk cutter rolls which are placed respectively on both sides of the metal sheet are arranged with being shifted in phase from the valleys of the disk cutters of another disk cutter roll.

[0035] According to the invention set forth in claim 2, since the valleys of the disk cutters are shifted in phase, one or more wires are pressed by the ridges to be bent in a ridge-like shape at the tip end of a drawn-out portion which is pressed by an end of the shifted valley to be drawn out in a substantially straight manner from a node. In the wires which are bent via the drawn-out portion, therefore, tensile stress produced during a developing process is dispersed, and hence the wire can be prevented from being easily corroded.

[0036] The invention set forth in claim 3 provides a method of producing a grid for a battery plate in which a metal sheet is passed between two rotating disk cutter rolls in each of which a plurality of disk cutters are placed on a same shaft with forming a gap therebetween, each of the disk cutters being configured by: alternately forming ridges which protrude in a ridge-like shape toward an outer peripheral side, and valleys composed of a circumferential face or a flat face along a circumferential direction on a peripheral side face of a disk; and forming grooves which are opened in an outer peripheral end and in every other valley alternately formed in both faces of the disk, in peripheral edges of both the faces of the disk, the disk cutter rolls being opposed to each other in a manner that the ridges of the disk cutters of one of the disk cutter rolls are placed in the gaps of the disk cutters of another disk cutter roll, whereby slits each configured by a cut elongating in a longitudinal direction are formed in the metal sheet, wherein

[0037] a length in a circumferential direction of the valleys of the disk cutters of the disk cutter roll which is placed on one side of the metal sheet is larger than a length of the valleys of the disk cutters of the disk cutter roll which is placed on another side of the metal sheet.

[0038] According to the invention set forth in claim 3, since the valleys of the disk cutters are different in length in the circumferential direction, one or more wires are pressed by the ridges to be bent in a ridge-like shape at the tip end of a drawn-out portion which is pressed by an end of the longer valley to be drawn out in a substantially straight manner from a node. In the wires which are bent via the drawn-out portion, therefore, tensile stress produced during a developing process is dispersed, and hence the wires can be prevented from being easily corroded.

[0039] The invention set forth in claim 4 provides a method of producing a grid for a battery plate in which a metal sheet is passed between two rotating disk cutter rolls in each of which a plurality of disk cutters are placed on a same shaft with forming a gap therebetween, each of the disk cutters being configured by: alternately forming ridges which protrude in a ridge-like shape toward an outer peripheral side, and valleys composed of a circumferential face or a flat face along a circumferential direction on a peripheral side face of a disk; and forming grooves which are opened in an outer peripheral end and in every other valley alternately formed in both faces of the disk, in peripheral edges of both the faces of the disk, the disk cutter rolls being opposed to each other in a manner that the ridges of the disk cutters of one of the disk cutter rolls are placed in the gaps of the disk cutters of another disk cutter roll, whereby slits each configured by a cut elongating in a longitudinal direction are formed in the metal sheet, wherein

[0040] the grooves of the disk cutters of the disk cutter roll(s) which is placed on one side or both sides of the metal sheet are opened only in a part of a whole circumferential length of the valleys.

[0041] According to the invention set forth in claim 4, since the grooves of the disk cutters are opened only in a part of the whole length of the valleys, the slits are formed also by the valleys other than the openings, and one or more wires are pressed by the ridges to be bent in a ridge-like shape at the tip end of a drawn-out portion which is drawn out in a substantially straight manner from a node. In the wires which are bent via the drawn-out portion, therefore, tensile stress produced during a developing process is dispersed, and hence the wires can be prevented from being easily corroded.

[0042] The invention set forth in claim 5 provides a method of producing a grid for a battery plate in which a metal sheet is passed between two rotating disk cutter rolls in each of which a plurality of disk cutters are placed on a same shaft with forming a gap therebetween, each of the disk cutters being configured by: alternately forming ridges which protrude in a ridge-like shape toward an outer peripheral side, and valleys composed of a circumferential face or a flat face along a circumferential direction on a peripheral side face of a disk; and forming grooves which are opened in an outer peripheral end and in every other valley alternately formed in both faces of the disk, in peripheral edges of both the faces of the disk, the disk cutter rolls being opposed to each other in a manner that the ridges of the disk cutters of one of the disk cutter rolls are placed in the gaps of the disk cutters of another disk cutter roll, whereby slits each configured by a cut elongating in a longitudinal direction are formed in the metal sheet, wherein

[0043] two or more of settings are made, the settings including: setting in which the valleys of the disk cutters of one of the disk cutter rolls which are placed on both sides of the metal sheet are arranged with being shifted in phase from the valleys of the disk cutters of another disk cutter roll; setting in which a length in a circumferential direction of the valleys of the disk cutters of the disk cutter roll which is placed on the one side of the metal sheet is larger than a length of the valleys of the disk cutters of the disk cutter roll which is placed on the other side of the metal sheet; and setting in which the grooves of the disk cutters of the disk cutter roll(s) which is placed on the one side or both the sides of the metal sheet are opened only in a part of a whole circumferential length of the valleys.

[0044] According to the invention set forth in claim 5, two or more kinds of the settings in which wires are pressed by protrusions to be bent in a ridge-like shape at the tip end of a drawn-out portion which is pressed by an end of the drawn-out portion that is drawn out in a substantially straight manner from a node are combinedly made. In the wires which are bent via the drawn-out portion, therefore, tensile stress produced during a developing process is dispersed, and hence the wires can be prevented from being easily corroded.

[0045] Means for Solving Problem (2)

[0046] The invention set forth in claim 6 provides a method of producing a grid for a battery plate wherein slits in which a small bent portion is formed between a node and a fence-like portion are formed in a metal sheet by using disk cutters of a rotary expander in each of which a plurality of ridges an apex of which is shifted toward a front side in a rotational direction protrude with forming a gap therebetween toward an outer circumference from a disk-like circumferential face at equal angular intervals, a small slope is interposed between a valley constituting a peripheral side face between two of the ridges, and at least a front slope of a peripheral side face of a ridge which is rearward adjacent to the valley, thereby connecting peripheral side faces, the small slope having an inclination angle which is between angles of the two faces, and grooves which are formed at equal angular intervals in peripheral edges of both disk-like faces are formed in every other gap face and opened alternately in both the faces.

[0047] According to the invention set forth in claim 6, since, in the disk cutter of the rotary expander, a small slope is interposed between each of the valleys and the slope of each of the ridges, the portion between the valley and the slope of the ridge is bent in two steps via the small slope, and the bending angles are gentle. When slits are formed in a metal sheet, therefore, the rising part of the fence-like portion between slits which are pressed by ridges of the disk cutters 1 to protrude from a node in a ridge-like shape is not bent by a steep angle, and can be bent in two steps via the small slope, so that edges of meshes which are formed by developing the slits are prevented from being easily corroded by electrolyte. In the production method of the invention, particularly, at least the bending angle which is formed by the valley and the slope of the ridge that is rearward adjacent thereto, and which is to be originally steep can be made gentle. Therefore, corrosion and a crack of corrosion in a node can be effectively prevented from occurring.

[0048] The invention set forth in claim 7 provides a method of producing a grid for a battery plate wherein slits in which a portion between a node and a fence-like portion is curved are formed in a metal sheet by using disk cutters of a rotary expander in each of which a plurality of ridges an apex of which is shifted toward a front side in a rotational direction protrude with forming a gap therebetween toward an outer circumference from a disk-like circumferential face at equal angular intervals, a curved face is interposed between a valley constituting a peripheral side face between two of the ridges, and at least a front slope of a peripheral side face of a ridge which is rearward adjacent to the valley, thereby connecting peripheral side faces, the curved face having a contact face of an inclination angle which is between angles of the two faces, and grooves which are formed at equal angular intervals in peripheral edges of both disk-like faces are formed in every other gap face and opened alternately in both the faces.

[0049] According to the invention set forth in claim 7, since, in the disk cutter of the rotary expander, a curved face is interposed between each of the valleys and the slope of each of the ridges, the portion between the valley and the slope of the ridge is smoothly bent via the curved face. When slits are formed in a metal sheet, therefore, the rising part of the fence-like portion between slits which are pressed by ridges of the disk cutters 1 to protrude from a node in a ridge-like shape is not angularly bent, and can be bent smoothly in, for example, a rounded manner, so that edges of meshes which are formed by developing the slits are prevented from being easily corroded by electrolyte. In the production method of the invention, particularly, at least the edge which is formed by the valley and the slope of the ridge that is rearward adjacent thereto, and which is to be originally steeply bent can be smoothed. Therefore, corrosion and a crack of corrosion in a node can be effectively prevented from occurring.

[0050] The invention set forth in claim 8 provides a method of producing a grid for a battery plate wherein slits in which a node is inclined are formed in a metal sheet by using disk cutters of a rotary expander in each of which a plurality of ridges an apex of which is shifted toward a front side in a rotational direction protrude with forming a gap therebetween toward an outer circumference from a disk-like circumferential face at equal angular intervals, a valley constituting a peripheral side face between two of the ridges is formed into a face which is more inclined toward a center as being more forward than a contact face contacting with a circumferential face in which all contacting faces contacting with the valley have a same angular position at a center of a rotation shaft, and grooves which are formed at equal angular intervals in peripheral edges of both disk-like faces are formed in every other gap face and opened alternately in both the faces.

[0051] According to the invention set forth in claim 8, since the valley between the ridges of the disk cutter used in the rotary expander is inclined toward the center as being more forward in the rotational direction, the bending angle formed by the valley and the steep slope of the ridge that is rearward adjacent thereto is made gentle, and that formed by the valley and the gentle slope of the ridge that is forward adjacent thereto is made steep. Consequently, the difference between the angles formed by the valley between the ridges and the slopes of the ridges that are respectively adjacent thereto on both the sides can be reduced. When slits are formed in a metal sheet, therefore, a node is inclined, and a phenomenon that only the rear side of the fence-like portion between slits is bent by a steep angle does not occur. As a result, the bending angles of the rear and front sides are averaged, whereby the edges can be prevented from being easily corroded by electrolyte. When the valley is configured by using a face which is formed by inclining a circumferential face, the angle formed by contact faces of the circumferential face can be always made constant. Alternatively, the valley may be configured by an inclined flat face or another curved face.

[0052] The invention set forth in claim 9 provides a method of producing a grid for a battery plate in which a plate is produced by a rotary expander for forming slits in a metal sheet by using disk cutters in each of which a plurality of ridges an apex of which is shifted toward a front side in a rotational direction protrude with forming a gap therebetween toward an outer circumference from a disk-like circumferential face at equal angular intervals, and grooves which are formed at equal angular intervals in peripheral edges of both disk-like faces are formed in every other valley constituting a peripheral side face between the ridges, and opened alternately in both the faces, wherein

[0053] each of the valleys of the disk cutter is formed into a face which is more inclined toward a center as being more forward than a contact face contacting with a circumferential face in which all contacting faces contacting with the valley have a same angular position at a center of a rotation shaft of the disk cutter.

[0054] According to the invention set forth in claim 9, since the valley between the ridges of the disk cutter is inclined toward the center as being more forward in the rotational direction, the bending angle formed by the valley and the steep slope of the ridge that is rearward adjacent thereto is made gentle, and that formed by the valley and the gentle slope of the ridge that is forward adjacent thereto is made steep. Consequently, the difference between the angles formed by the valley between the ridges and the slopes of the ridges that are respectively adjacent thereto on both the sides can be reduced. Therefore, a phenomenon that only the rear side of the fence-like portion between slits of the metal sheet is bent by a steep angle does not occur. As a result, the bending angles of the rear and front sides are averaged, whereby the edges can be prevented from being easily corroded by electrolyte. When the valley is configured by using a face which is formed by inclining a circumferential face, the angle formed by contact faces of the circumferential face can be always made constant. Alternatively, the valley may be configured by an inclined flat face or another curved face.

[0055] The invention set forth in claim 10 is characterized in that the valley is formed into a face which is more inclined by 1° or more toward the center as being more forward than the contact face contacting with the circumferential face in which all contacting faces contacting with the valley have a same angular position at the center of the rotation shaft of the disk cutter.

[0056] According to the invention set forth in claim 10, since the valley between the ridges of the disk cutter has an inclination of 10 or more, the bending angle formed by the valley and the steep slope of the ridge that is rearward adjacent thereto can be surely made gentle.

[0057] The invention set forth in claim 11 is characterized in that only a face of the valley excluding a front end portion is formed into a face which is more inclined toward the center as being more forward than the contact face contacting with the circumferential face in which all contacting faces contacting with the valley have a same angular position at the center of the rotation shaft of the disk cutter.

[0058] The valley between the ridges of the disk cutter may be configured by, for example, an inclined flat face in place of a face which is formed by inclining a circumferential face. When such a flat face has a small inclination angle, there is a case where, in the vicinity of a portion where the flat face is adjacent to the front ridge, the contact face of the circumferential face is more inclined toward the center as being more forward. In some cases, the portion where the valley is adjacent to the front ridge may be rounded, or a small slope having an intermediate inclination angle may be interposed between the valley and the front ridge. A contact face of the rounded face or the small slope may be inclined more outward than a contact face of a circumferential face at the same angular position. According to the invention set forth in claim 11, however, the contact face of the valley between the ridges of the disk cutter excluding such a front end portion is more inclined toward the center as being more forward. Therefore, at least the bending angle formed by the valley and the steep slope of the ridge that is rearward adjacent thereto can be surely made gentle. In some cases, also the portion where the valley is adjacent to the rear ridge may be rounded, or a small slope having an intermediate inclination angle may be interposed between the valley and the rear ridge. A contact face of the rounded face or the small slope is always more inclined toward the center than a contact face of a circumferential face at the same angular position.

[0059] The invention set forth in claim 12 is characterized in that the circumferential face serving as a reference of inclination of the valley is a flat face connecting together cross lines between the circumferential face and the slopes of the ridges on both the sides.

[0060] A conventional valley is sometimes configured by a flat face in place of a face extending along a circumferential face. In such a flat face, the rear half is a face which is slightly inclined toward the center in a larger degree as being more forward than a contact face contacting with a circumferential face at the same angular position, but the front half is a face which is slightly inclined toward the center in a larger degree as being more rearward than a contact face contacting with a circumferential face at the same angular position. However, this can make gentle the angle formed by the valley and the slope of the ridge, only by a small degree, and there is little difference between the case where the valley is configured by a flat face, and that where the valley is configured by a face extending along a circumferential face. By contrast, according to the invention set forth in claim 12, the valley between the ridges is more inclined than the flat face, and hence at least the bending angle formed by the valley and the steep slope of the ridge that is rearward adjacent thereto can be surely made gentle.

[0061] Means for Solving Problem (3)

[0062] The invention set forth in claim 13 provides a method of producing a grid for a battery plate in which a rotary expander is used for forming a large number of zigzag slits in a metal sheet by passing the metal sheet between two or more opposed disk cutter rolls, each of the disk cutter rolls being configured by placing a plurality of disk cutters on a same shaft with forming a gap therebetween, each of the disk cutters being configured by: alternately forming ridges in which a peripheral side face protrudes in a ridge-like shape toward an outer periphery from a reference circumferential face of a predetermined radius, and valleys in which a peripheral side face composed of a face substantially extending along the reference circumferential face is formed, in a whole periphery of a peripheral edge of a disk, the reference circumferential face being centered at an axis of the disk; and, for each of the valleys, forming a groove which is opened in a peripheral side face of the valley, in a peripheral edge portion of one of disk faces in which valleys that are adjacent to each other via a ridge are formed in an oppositely reverse manner, wherein, in each of the disk cutters, an inclined face is formed in peripheral side faces which extend from apexes of ridges formed on both sides of each of the valleys to the valley, the inclined face more approaching the axis as being nearer to the disk face in which the groove of the valley is formed.

[0063] According to the invention set forth in claim 13, since the inclined face is formed in the peripheral side face of the ridge of the disk cutters, thin wires which are configured between adjacent slits are formed in a ridge-like shape in a state where the wires are pretwisted along the inclined face when slits are formed in a metal sheet by pressing of the ridge. Furthermore, the wires are inclined toward the groove. During the developing process, therefore, the node is pulled by the wires to be set to a direction which is opposite to the twisting direction. As a result, concentration of torsion stress in the vicinity of the apexes of the wires during the developing process can be reduced.

[0064] The inclined face which more approaches the axis as being nearer to the disk face means that a contact face of the inclined face is inclined so as to more approach the axis of the disk cutter as being nearer to the disk face, or means that the inclined face may have a part where a contact face is parallel to the axis but is not allowed to have a part where a contact face is inclined toward the outer peripheral side.

[0065] Preferably, the inclined face is formed from a position of a peripheral side face of a ridge, to a valley, the position being higher than the valley by one third or more of a height in a radial direction of the disk cutter extending from the valley to an apex of the ridge. Conventionally, torsion stress is concentrated on the vicinity of an apex of a wire. Therefore, it is preferable to form the inclined face of a ridge of a disk cutter so as to extend as far as possible to the vicinity of the apex. When the inclined face is formed so as to extend from a level which is higher by one third or more of the ridge to the valley, therefore, the twisting which is previously formed in the wire can surely exert an effect.

[0066] Preferably, the inclination angle of the inclined face is equal to or smaller than 40° with respect to the reference circumferential face. When the inclination angle of the inclined face is 40°, the angle of an edge between the inclined face and the disk face can be set to 60° or more, and hence the metal sheet can be surely cut.

[0067] The grid for a battery plate of the invention set forth in claim 14 is characterized in that the grid is produced by the production method of claim 13.

[0068] According to the invention set forth in claim 14, since concentration of torsion stress in the vicinity of the apexes of the wires during developing process can be reduced, a grid for a battery plate in which rupture or breakage hardly occurs is obtained.

[0069] Means for Solving Problem (4)

[0070] The invention set forth in claim 15 provides a method of producing a grid for a battery plate in which a plurality of parallel slits are cut in a metal sheet into a zigzag pattern along an advancing direction of the metal sheet, wires which are formed by slits that are adjacent in a width direction of the metal sheet are elastically deformed in a ridge-like shape in both front and ewe directions from a face of the metal sheet, flat regions which are formed by non-slit portions are formed to become nodes of the wires, and the metal sheet is developed in the width direction, thereby forming meshes, wherein the slits which are cut into a zigzag pattern are formed by passing the metal sheet through a roll pair in which rolls are opposed to each other, each of the rolls is configured by stacking disk cutters each having ridges and valleys, the ridges protruding at regular intervals from a circumference of the disk cutter, and, in the disk cutter, grooves are disposed in a thickness direction in each of the valleys between the ridges and alternately in both disk faces corresponding to the nodes, and chamfered portions are disposed in an outer peripheral portion of a peripheral side face of the disk cutter, the outer peripheral portion excluding at least the ridges, the chamfered portions being lowered as being respectively nearer to the faces in which the grooves are disposed.

[0071] The invention set forth in claim 16 is characterized in that the chamfered portions between the peripheral side face of the disk cutter and the disk faces of the disk cutter in which the grooves are formed are planer or curved chamfered portions.

[0072] The invention set forth in claim 17 provides a battery comprising a grid for a battery plate which is produced by the method of claim 15 or 16.

[0073] Means for Solving Problem (5)

[0074] The invention set forth in claim 18 provides a method of producing a grid for a battery plate in which a rotary expander is used for forming a large number of zigzag slits in a metal sheet by passing the metal sheet between two or more opposed disk cutter rolls, each of the disk cutter rolls being configured by placing a plurality of disk cutters on a same shaft with forming a gap therebetween, each of the disk cutters being configured by: alternately forming ridges in which a peripheral side face protrudes in a ridge-like shape toward an outer periphery from a reference circumferential face of a predetermined radius, and valleys in which a peripheral side face composed of a face substantially extending along the reference circumferential face is formed, in a whole periphery of a peripheral edge of a disk, the reference circumferential face being centered at a rotation axis of the disk; and, for each of the valleys, forming a groove which is opened in a peripheral side face of the valley, in a peripheral edge portion of one of disk faces in which valleys that are adjacent to each other via a ridge are formed in an oppositely reverse manner, wherein, among the disk cutter rolls, a disk cutter roll which is opposed to a disk cutter roll having a disk cutter that is disposed outermost is provided with a disk-like endmost disk cutter that is placed more outward than the outermost disk cutter, and a peripheral side face which is recessed toward a center with respect to the reference circumferential face is formed in a valley (hereinafter, referred to as “endmost node forming valley”) which corresponds to a valley in a disk cutter of another disk cutter roll that is opposed via the metal sheet, among valleys of the endmost disk cutter (in the endmost disk cutter, peripheral edge portions respectively corresponding to valleys of another disk cutter of a same disk cutter roll are referred to as “valleys”), a groove being formed in a disk face in the groove of the disk cutter of the other disk cutter roll, the disk face directed to the endmost disk cutter.

[0075] In a usual node, deformation of a degree which is larger than the thickness of a metal sheet is produced because peripheral side faces of valleys of both disk cutters of disk cutter rolls which are opposed via the metal sheet press the metal sheet from both the sides while exceeding the cutting plane that is in the center between the axes of the disk cutter rolls. By contrast, according to the invention set forth in claim 18, the peripheral side faces of the endmost node forming valleys of the endmost disk cutter are recessed with respect to the reference circumferential face. Even when peripheral side faces of valleys of disk cutters of disk cutter rolls which are opposed via a metal sheet press an end portion of the endmost node while exceeding the cutting plane, therefore, the peripheral side faces of the endmost node forming valleys of the endmost disk cutter press the basal portion of the endmost node with advancing in front of the cutting plane at the most. Consequently, deformation of the endmost node is reduced, so that wires drawn out from the node can be surely prevented from being easily broken.

[0076] Preferably, the peripheral side face of the endmost node forming valley is recessed toward the center with respect to a circumferential face of a predetermined radius by a degree which is not smaller than 30% and not larger than 70% of a thickness of the metal sheet. When the peripheral side face of the endmost node forming valley is recessed by 20% of the sheet thickness, for example, deformation of the endmost node exceeds 80% of the sheet thickness, and is not largely different from that of the prior art. When the peripheral side face of the endmost node forming valley is recessed by 80% of the sheet thickness, deformation of the endmost node can be restricted to a degree which slightly exceeds about 20% of the sheet thickness. In the valleys of the endmost disk cutter other than the endmost node forming valleys, slits are formed by pressing a metal sheet while exceeding the cutting plane between the disk cutter rolls, and, with respect to also the ridges (in the case of the endmost disk cutter, peripheral edge portions respectively corresponding to ridges of another disk cutter of the same disk cutter roll are referred to as “ridges”), pressing is usually conducted in a similar manner. Therefore, a step corresponding to about 80% of the sheet thickness is produced between these portions and the endmost node forming valleys. By contrast, when the recess of the peripheral side face of each of the endmost node forming valleys is set to about 50% of the sheet thickness, deformation of the endmost node and the step between the node and the surrounding metal sheet can have an optimum size of about 50% of the sheet thickness. Consequently, it is preferable to form a recess which is not smaller than 30% and not larger than 70% of the sheet thickness.

[0077] In the valleys of the endmost disk cutter, it is not always necessary to form a groove. In the valleys of the endmost disk cutter other than the endmost node forming valleys, the grooves are formed in the disk face of the endmost disk cutter which is outward directed. Therefore, it is entirely unnecessary to form such valleys, except the case where parts are shared by the endmost disk cutter and that which is placed in the opposite outer end. By contrast, the grooves of the endmost node forming valleys of the endmost disk cutter are formed in the disk face of the endmost disk cutter which is inward directed, and a space for forming endmost nodes is required between the grooves, and those of valleys of a disk cutter which is opposed to the endmost disk cutter via the metal sheet. In a usual case, therefore, it is preferable to dispose grooves of the endmost node forming valleys. In the invention set forth in claim 18, the peripheral side faces of the endmost node forming valleys are recessed. When the recesses are formed to be sufficiently large, therefore, an enough space can be ensured between the valleys and the grooves of the valleys of the opposed disk cutter, and hence forcible deformation is not produced in the endmost nodes, with the result that formation of grooves is not always necessary.

[0078] Preferably, an inclined face which more approaches a center as being nearer to an outer side is formed in each of peripheral side faces of the valleys and/or the ridges of the endmost disk cutter other than the endmost node forming valleys. In the valleys of the endmost disk cutter other than the endmost node forming valleys, slits are formed by pressing the metal sheet while exceeding the cutting plane between the disk cutter rolls. Also in the ridges, usually, pressing is conducted in a similar manner. Therefore, a step is produced between these portions and the endmost node forming valleys in which the peripheral side face is recessed, so that step-like undulation may be formed in the frame portion of the metal sheet. When each of the peripheral side faces of the valleys and the ridges other than the endmost node forming valleys is formed as an inclined face, the frame portion of the metal sheet can be gently bent.

[0079] In each of the ridges of the endmost disk cutter, preferably, a peripheral side face of the reference circumferential face or a peripheral side face which is nearer to the center than the reference circumferential face is formed. When the peripheral side faces of the ridges of the endmost disk cutter protrude in a ridge-like shape in the same manner as those of a usual disk cutter, the edge of the frame portion of the metal sheet is unnecessarily vertically pressed to cause deformation, because no slits are formed outside the ridges. Since the ridge-like protruding peripheral side face of each of the ridges of a usual disk cutter presses the metal sheet while greatly exceeding the cutting plane between the disk cutter rolls, the metal sheet can be cut in many cases, even when the peripheral side face of each of the valleys of the endmost disk cutter which is opposed to the usual disk cutter does not exceed the cutting plane. Therefore, the peripheral side face of each of the valleys of the endmost disk cutter can be formed in the reference circumferential face. When a peripheral side face which is nearer to the center at a degree similar to the peripheral side faces of the endmost node forming valleys is formed, for example, the frame portion of the metal sheet can be prevented from largely undulating.

[0080] The method of producing a grid for a battery plate set forth in claim 19 is characterized in that an inclined face is formed in the peripheral side face of the endmost node forming valley, the inclined face being nearer to the center as being more inward.

[0081] In the case where a groove is not formed in the endmost node forming valley, when the peripheral side face is recessed by a small degree from the reference circumferential face, the endmost node is deformed only by means of the space in the recess of the valley of the disk cutter which is opposed via the metal sheet, and hence there is the possibility that, when the amount of deformation is large, the endmost node is deformed in an extremely abrupt manner. According to the invention set forth in claim 19, an inclined face is formed in the peripheral side face of the endmost node forming valley, and hence the endmost node can be gently deformed along the inclined face. Even in the case where a groove is formed in the endmost node forming valley, the deformation of the endmost node can be made more gentle by the formation of an inclined face in the peripheral side face.

[0082] The grid for a battery plate of the invention set forth in claim 20 is characterized in that the grid is produced by the production method of claim 18 or 19.

[0083] According to the invention set forth in claim 20, a grid for a battery plate in which wires drawn out from the endmost nodes are hardly broken is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0084]FIG. 1 is a partial enlarged perspective view showing a first example of a first embodiment of the invention, and showing the vicinity of a node of a grid in an enlarged manner;

[0085]FIG. 2 is a partial enlarged schematic view showing the first example of the first embodiment of the invention, and schematically showing in an enlarged manner a portion where disk cutters which are vertically placed overlap with each other;

[0086]FIG. 3 is a partial enlarged schematic view showing a second example of the first embodiment of the invention, and schematically showing in an enlarged manner a portion where disk cutters which are vertically placed overlap with each other;

[0087]FIG. 4 is a partial enlarged perspective view showing the second example of the first embodiment of the invention, and showing in an enlarged manner the vicinity of a node of a grid;

[0088]FIG. 5 is a partial enlarged schematic view showing a third example of the first embodiment of the invention, and schematically showing in an enlarged manner a portion where upper and lower phase-shifted disk cutters overlap with each other;

[0089]FIG. 6 is a partial enlarged perspective view showing the third example of the first embodiment of the invention, and showing in an enlarged manner the vicinity of a node of a grid which is produced by the phase-shifted disk cutters;

[0090]FIG. 7 is a partial enlarged schematic view showing a fourth example of the first embodiment of the invention, and schematically showing in an enlarged manner a portion where disk cutters which are vertically placed overlap with each other;

[0091]FIG. 8 is a partial enlarged perspective view showing the fourth example of the first embodiment of the invention, and showing in an enlarged manner the vicinity of a node of a grid;

[0092]FIG. 9 is a partial enlarged schematic view showing a fifth example of the first embodiment of the invention, and schematically showing in an enlarged manner a portion where disk cutters which are vertically placed with shifting grooves to one side overlap with each other;

[0093]FIG. 10 is a partial enlarged perspective view showing the fifth example of the first embodiment of the invention, and showing in an enlarged manner the vicinity of a node of a grid which is produced by the disk cutters having grooves shifted to one side;

[0094]FIG. 11 is a partial enlarged schematic view showing a sixth example of the first embodiment of the invention, and schematically showing in an enlarged manner a portion where disk cutters which are vertically placed with shifting grooves in opposite directions overlap with each other;

[0095]FIG. 12 is a partial enlarged perspective view showing the sixth example of the first embodiment of the invention, and showing in an enlarged manner the vicinity of a node of a grid which is produced by the disk cutters having grooves shifted in opposite directions;

[0096]FIG. 13 is a partial enlarged schematic view showing a seventh example of the first embodiment of the invention, and schematically showing in an enlarged manner a portion where upper and lower phase-shifted disk cutters overlap with each other;

[0097]FIG. 14 is a partial enlarged perspective view showing the seventh example of the first embodiment of the inventions, and showing in an enlarged manner the vicinity of a node of a grid which is produced by the phase-shifted disk cutters;

[0098]FIG. 15 is a partial enlarged front view showing a second embodiment of the invention, and showing a valley of a disk cutter;

[0099]FIG. 16 is a partial enlarged front longitudinal section view showing the second embodiment of the invention, and showing a fence-like portion between slits protruding in a ridge-like shape in a metal sheet;

[0100]FIG. 17 is a partial enlarged front view showing an embodiment of the invention, and showing a case where, in place of a small slope, a curved faces is interposed in both sides of a gap face of a disk cutter;

[0101]FIG. 18 is a partial enlarged front view showing a third embodiment of the invention, and showing an inclined valley of a disk cutter;

[0102]FIG. 19 is a partial enlarged front longitudinal section view showing the third embodiment of the invention, and showing a fence-like portion between slits protruding in a ridge-like shape in a metal sheet;

[0103]FIG. 20 is a front view showing a fourth embodiment of the invention, and showing the whole of a disk cutter, and a peripheral edge of the disk cutter in an enlarged manner;

[0104]FIG. 21 is a partial enlarged perspective view showing the fourth embodiment of the invention, and showing inclined faces formed in peripheral side faces of ridges which are opposed across a valley of the disk cutter;

[0105]FIG. 22 is a partial enlarged side longitudinal section view showing the fourth embodiment of the invention, and showing a slit forming step of a rotary expander and illustrating a manner in which wires of a metal sheet are twisted with being pressed by the inclined faces formed in ridges of disk cutters of upper and lower disk cutter rolls;

[0106]FIG. 23 is a partial enlarged perspective view showing the fourth embodiment of the invention, and showing a lead sheet and illustrating a node formed in the slit forming step, and four wires connected thereto;

[0107]FIG. 24 is a partial enlarged perspective view showing the fourth embodiment of the invention, and showing another first configuration example of the inclined faces formed in peripheral side faces of ridges which are opposed across a valley of the disk cutter;

[0108]FIG. 25 is a partial enlarged perspective view showing the fourth embodiment of the invention, and showing another second configuration example of the inclined faces formed in peripheral side faces of ridges which are opposed across a valley of the disk cutter;

[0109]FIG. 26 is a partial enlarged perspective view showing the fourth embodiment of the invention, and showing another third configuration example of the inclined faces formed in peripheral side faces of ridges which are opposed across a valley of the disk cutter;

[0110]FIG. 27(a) is a schematic view showing a first example of a fifth embodiment of the invention, and showing a section shape taken along a plane passing through the disk center of a disk cutter and perpendicular to a disk face in the case where a node is formed in a metal sheet by a cutting tool, and FIG. 27(b) is a partial perspective view showing the vicinity of a valley of the disk cutter of the fifth embodiment;

[0111]FIG. 28(a) is a schematic view showing a second example of the fifth embodiment of the invention, and showing a section shape taken along a plane passing through the disk center of a disk cutter and perpendicular to a disk face in the case where a node is formed in a metal sheet by a cutting tool, and FIG. 28(b) is a partial perspective view showing the vicinity of a valley of the disk cutter of the fifth embodiment;

[0112]FIG. 29(a) is a schematic view showing a third example of the fifth embodiment of the invention, and showing a section shape taken along a plane passing through the disk center of a disk cutter and perpendicular to a disk face in the case where a node is formed in a metal sheet by a cutting tool, and FIG. 29(b) is a partial perspective view showing the vicinity of a valley of the disk cutter of the fifth embodiment;

[0113]FIG. 30 is a partial enlarged front longitudinal section view showing a sixth embodiment of the invention, and showing a process of forming slits in a metal sheet by disk cutters of upper and lower disk cutter rolls;

[0114]FIG. 31 is a side view showing the sixth embodiment of the invention, and showing the configuration of an endmost disk cutter;

[0115]FIG. 32 is a partial enlarged perspective view showing the sixth embodiment of the invention, and showing the configuration of the endmost disk cutter;

[0116]FIG. 33 is a partial enlarged perspective view showing the sixth embodiment of the invention, and showing the vicinity of an endmost node in a grid which is obtained by developing slits formed in a metal sheet;

[0117]FIG. 34 is a partial enlarged front longitudinal section view showing the sixth embodiment of the invention, and showing a process of forming slits in a metal sheet by using an endmost disk cutter in which inclined faces are formed in peripheral side faces of ridges;

[0118]FIG. 35 is a partial enlarged front longitudinal section view showing the sixth embodiment of the invention, and showing a process of forming slits in a metal sheet by using an endmost disk cutter in which peripheral side faces of valleys are configured as a circumferential face;

[0119]FIG. 36 is a partial enlarged front longitudinal section view showing the sixth embodiment of the invention, and showing a process of forming slits in a metal sheet by using an endmost disk cutter in which peripheral side faces of valleys are recessed;

[0120]FIG. 37 is a front view showing a prior art example, and showing the configuration of a disk cutter and a peripheral edge of the disk cutter;

[0121]FIG. 38 is a front view showing a prior art example, and showing a step of forming slits in a metal sheet by a disk cutter in a rotary expander;

[0122]FIG. 39 is a partial enlarged side longitudinal section view showing a prior art example, and showing an arrangement of disk cutters in a rotary expander;

[0123]FIG. 40 is a partial enlarged perspective view showing a prior art example, and showing a grid which is obtained by forming slits in a metal sheet and developing the slits;

[0124]FIG. 41 is a partial enlarged view showing a prior art example, and showing ridges and valleys of a disk cutter;

[0125]FIG. 42 is a partial enlarged side longitudinal section view showing a prior art example, and showing a fence-like portion between slits protruding in a ridge-like shape in a metal sheet;

[0126]FIG. 43 is a partial enlarged plan view showing a prior art example, and showing a grid which is formed by developing slits of a metal sheet into meshes;

[0127]FIG. 44 is a partial enlarged perspective view showing a prior art example, and showing a metal sheet illustrating a node formed in the slit forming step, and wires connected thereto;

[0128]FIG. 45 is a partial enlarged perspective view showing a prior art example, and showing a grid which is obtained by, in a developing step, developing a metal sheet in which slits are formed in a slit forming step;

[0129]FIG. 46(a) is a schematic view showing a prior art example, and showing a section shape taken along a plane passing through the disk center of a disk cutter and perpendicular to a disk face in the case where a node is formed in a metal sheet by a cutting tool, and FIG. 46(b) is a partial section view showing the node formed by the cutter;

[0130]FIG. 47 is a partial enlarged front longitudinal section view showing a prior art example, and showing a process of forming slits in a metal sheet by disk cutters of upper and lower disk cutter rolls;

[0131]FIG. 48 is a side view showing a prior art example, and showing the configuration of an endmost disk cutter;

[0132]FIG. 49 is a partial enlarged perspective view showing a prior art example, and showing the configuration of the endmost disk cutter; and

[0133]FIG. 50 is a partial enlarged perspective view showing a prior art example, and showing the vicinity of an endmost node in a grid which is obtained by developing slits formed in a metal sheet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0134] Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings.

[0135] Embodiment (1) of the Invention

[0136]FIGS. 1 and 2 show a first example of a first embodiment of the invention. FIG. 1 is a partial enlarged perspective view showing the vicinity of a node of a grid in an enlarged manner, and FIG. 2 is a partial enlarged schematic view schematically showing in an enlarged manner a portion where disk cutters which are vertically placed overlap with each other. The components having the same functions as those of the prior art example shown in FIGS. 37 to 50 are denoted by the identical reference numerals.

[0137] In the same manner as the prior art example, in the embodiment, a grid which is to be used in a battery plate of a lead storage battery will be described, and also a method of producing the grid for a battery plate from the metal sheet 2 by a rotary expander will be described.

[0138] The embodiment is a case where, as shown in FIG. 2, the disk cutters 1, 1 which are vertically opposed to each other are changed in phase. A plurality of the upper and lower disk cutters 1, 1 are combined so as to be used as disk cutter rolls, respectively. In the disk cutters 1, 1 lengths in the circumferential direction of the valleys 1 b and the ridges 1 a are equal to each other. Conventionally, such disk cutters 1, 1 are placed and rotated while their phases coincide with each other so that the valleys 1 b, 1 b vertically overlap with each other without being mutually shifted. By contrast, in the embodiment, the phase of the disk cutter 1 which is placed in the upper side leads by a phase angle α. In the embodiment, namely, the upper disk cutter 1 is placed with being slightly shifted toward the front side in the rotational direction (indicated by the arrow in FIG. 2). In order to facilitate the understanding of the phase shifting, the upper and lower disk cutters 1, 1 in FIG. 2 are shown with being vertically separated from each other. In practice, the disk cutters are placed so closely that the valleys 1 b slightly overlap with each other. In FIG. 2, the circumferential faces of the disk cutters 1, 1 are shown with being developed to a horizontal plane.

[0139] When the metal sheet 2 is passed between the upper and lower disk cutters 1, 1 in the prior art which are not shifted in phase, the slits 2 a are formed by the overlapping portions between the upper and lower ridges 1 a, 1 a, and those between the upper and lower valleys 1 b, 1 b where the grooves 1 c, 1 c are opened with facing in opposite directions, and the nodes 2 c are formed by the overlapping portions between the upper and lower valleys 1 b where the grooves 1 c are opened with facing each other. The length of each node 2 c in the longitudinal direction (the advancing direction indicated by the arrow in FIG. 2) is equal to the length in the circumferential direction of each valley 1 b, i.e., the width of each groove 1 c.

[0140] By contrast, when the metal sheet 2 is passed between the disk cutters 1, 1 in the embodiment, the nodes 2 c are formed only by the portions where the upper and lower grooves 1 c, 1 c overlap with each other, because the openings of the grooves are shifted from each other, with the result that the length of the nodes 2 in the longitudinal direction is shorter than the length of the valleys 1 b and the width of the grooves 1 c. As shown in FIG. 1, in the rear side of each node 2 c in the longitudinal direction of the metal sheet 2, the wire 2 b (the left front one in the figure) which is downward pressed by the ridge 1 a of the upper disk cutter 1 that leads in phase is downward bent with starting immediately from the basal end of the node 2 c, and the wire 2 b (the left rear one in the figure) which is upward pressed by the ridge 1 a of the lower disk cutter 1 that lags in phase is upward bent at the tip end of a drawn-out portion 2 d which is rearward drawn out from the node 2 c in the longitudinal direction of the metal sheet 2. In the front side of the node 2 c in the longitudinal direction of the metal sheet 2, the wire 2 b (the right rear one in the figure) which is upward pressed by the ridge 1 a of the lower disk cutter 1 that lags in phase is upward bent with starting immediately from the basal end of the node 2 c, and the wire 2 b (the right front one in the figure) which is downward pressed by the ridge 1 a of the upper disk cutter 1 that leads in phase is downward bent at the tip end of a drawn-out portion 2 d which is forward drawn out from the node 2 c in the longitudinal direction of the metal sheet 2. The drawn-out portions 2 d are portions which fail to be completely formed as the node 2 c, because they are caused to remain flat by the valley 1 b of one of the disk cutters 1 in the same manner as the node 2 c, but the metal sheet 2 is pressed to be cut by the ridge 1 a of the other disk cutter 1 where no groove 1 c exists.

[0141] As a result, in the grid of the embodiment, among the four wires 2 b connected to the node 2 c, the two diagonal wires 2 b (the left front and right rear ones in the figure) are bent with starting immediately from the basal end of the node 2 c and diagonally elongate in the same manner as in the prior art example, but the remaining two wires 2 b (the left rear and right front ones in the figure) are bent at the tip ends of the drawn-out portions 2 d which are once drawn out from the basal end of the node 2 c in the longitudinal direction of the metal sheet 2, and then diagonally elongate. When the grid is stretched in the width direction of the metal sheet 2 to be developed, therefore, the tensile stress applied to the two wires 2 b which are drawn out and bent from the node 2 c via the drawn-out portions 2 d is dispersed to the whole drawn-out portions 2 d, so that, even after the developing process, the drawn-out portions 2 d can maintain the state where the portions are drawn out in a substantially longitudinal direction. FIG. 1 shows the grid after development. In practice, also in the grid which is immediately after the formation of the slits 2 a by the disk cutters 1, 1, the drawing out angles of the wires are made gentle, and there is no difference in the drawn-out portions 2 d before and after development. With respect to the two wires 2 b in which no drawn-out portion 2 d is disposed, therefore, the tensile stress during the developing process is concentrated in the basal end of the node 2 c, and hence there is the possibility that large distortion or rupture occurs. In the same manner as the prior art example, consequently, the wires are easily corroded by electrolyte during use of the storage battery. By contrast, in the two wires 2 b in which the drawn-out portion 2 d is disposed, large distortion or rupture does not occur, so that corrosion due to electrolyte hardly occurs. As a result, the possibility that a crack of such corrosion occurs in the wires 2 b can be reduced.

[0142] The embodiment can be implemented simply by using as they are the disk cutters 1 which are shown in the prior art example, and shifting the phases of the upper and lower disk cutters when the disk cutter rolls are to be disposed.

[0143]FIGS. 3 and 4 show a second example of the first embodiment of the invention. FIG. 3 is a partial enlarged schematic view schematically showing a portion where disk cutters which are vertically placed overlap with each other, and FIG. 4 is a partial enlarged perspective view showing the vicinity of a node of a grid in an enlarged manner.

[0144]FIGS. 5 and 6 show a third example of the first embodiment of the invention. FIG. 5 is a partial enlarged schematic view schematically showing in an enlarged manner a portion where upper and lower phase-shifted disk cutters overlap with each other, and FIG. 6 is a partial enlarged perspective view showing in an enlarged manner the vicinity of a node of a grid which is produced by the phase-shifted disk cutters. The components having the same functions as those of the first embodiment shown in FIGS. 1 and 2 are denoted by the identical reference numerals. In the same manner as FIG. 2, FIGS. 3 and 5 show the upper and lower disk cutters with being vertically separated from each other, and the circumferential faces are shown with being developed to a horizontal plane. In the same manner as FIG. 1, actually, FIGS. 4 and 6 show a grid which has been developed.

[0145] In the same manner as the first example, also in the second and third examples of the embodiment, a grid for a plate of a storage battery will be described, and also a method of producing the grid from the metal sheet 2 by the upper and lower disk cutters 1, 1 of the rotary expander will be described. In the embodiment, as shown in FIG. 3, the lengths of the valleys 1 b of the disk cutters 1, 1 which are vertically opposed to each other are different. In the embodiment, namely, the length Ld in the circumferential direction of the valley 1 b of the disk cutter 1 which is placed in the lower side is longer than the length Lu of the valley 1 b of the disk cutter 1 which is placed in the upper side. In accordance with the above, the width of the groove 1 c by which the groove is opened in each of the valleys 1 b of the lower disk cutter 1 is longer. In the lower disk cutter 1, the pitch of the valleys 1 b along the circumference is made equal to that of the upper disk cutter 1, by reducing the length of the ridges 1 a in the circumferential direction. Moreover, the phases of the upper and lower disk cutters 1 coincide with each other, so that each of the valleys 1 b of the upper disk cutter 1 overlaps just with the center of the whole length of the corresponding valley 1 b of the lower disk cutter 1.

[0146] When the metal sheet 2 is passed between the upper and lower disk cutters 1, 1, only the nodes 2 c the length of which is equal to the shorter width of the grooves 1 c of the upper disk cutter 1 are formed in the grid, because the widths of the upper and lower grooves 1 c, 1 c are different from each other. As shown in FIG. 4, in one side of each node 2 c in the width direction of the metal sheet 2, two wires (the front ones in the figure) which are downward pressed by the ridge 1 a of the upper disk cutter 1 having the shorter valleys 1 b are downward bent with starting immediately from the basal end of the node 2 c, and by contrast two wires (the rear ones in the figure) which are upward pressed by the ridge 1 a of the lower disk cutter 1 having the longer valleys 1 b are upward bent at the tip ends of the drawn-out portions 2 d which are frontward and backward drawn out from the node 2 c in the longitudinal direction of the metal sheet 2.

[0147] When the grid is stretched in the width direction of the metal sheet 2 to be developed, the tensile stress applied to the two wires 2 b which are drawn out and bent from the node 2 c via the drawn-out portions 2 d is dispersed to the whole drawn-out portions 2 d, so that, even after the developing process, the drawn-out portions 2 d can maintain the state where the portions are drawn out in a substantially longitudinal direction. In the two wires 2 b which are bent at the tip ends of the drawn-out portions 2 d, therefore, large distortion or rupture does not occur during the developing process, so that corrosion due to electrolyte hardly occurs. As a result, the possibility that a crack of corrosion occurs in the wires 2 b during use of the storage battery can be reduced.

[0148] In the second example, the case where the phases of the upper and lower disk cutters 1, 1 coincide with each other has been described. Alternatively, the phases may be shifted from each other. As shown in FIG. 5, for example, the lower disk cutter 1 may lead in phase so that the rear ends of the grooves 1 c, 1 c vertically coincide with each other. As a result, as shown in FIG. 6, the wire 2 b (the right rear front one in the figure) which is upward pressed by the ridge 1 a of the lower disk cutter 1 having the longer valleys 1 b is upward bent at the tip end of the drawn-out portion 2 d which is forward drawn out from the node 2 c in the longitudinal direction. The tensile stress applied to the wire 2 b during the developing process is dispersed to the whole drawn-out portion 2 d, whereby, although for one bar for each of the nodes 2 c, the possibility that a crack of corrosion due to electrolyte occurs in the wire 2 b during use of the storage battery can be reduced.

[0149]FIGS. 7 and 8 show a fourth example of the first embodiment of the invention. FIG. 7 is a partial enlarged schematic view schematically showing in an enlarged manner a portion where disk cutters which are vertically placed overlap with each other, and FIG. 8 is a partial enlarged perspective view showing in an enlarged manner the vicinity of a node of a grid. FIGS. 9 and 10 show a fifth example of the first embodiment of the invention. FIG. 9 is a partial enlarged schematic view schematically showing in an enlarged manner a portion where disk cutters which are vertically placed with shifting grooves to one side overlap with each other, and FIG. 10 is a partial enlarged perspective view showing in an enlarged manner the vicinity of a node of a grid which is produced by the disk cutters having grooves shifted to one side.

[0150]FIGS. 11 and 12 show a sixth example of the first embodiment of the invention. FIG. 11 is a partial enlarged schematic view schematically showing in an enlarged manner a portion where disk cutters which are vertically placed with shifting grooves in opposite directions overlap with each other, and FIG. 12 is a partial enlarged perspective view showing in an enlarged manner the vicinity of a node of a grid which is produced by the disk cutters having grooves shifted in opposite directions.

[0151]FIGS. 13 and 14 show a seventh example of the first embodiment of the invention. FIG. 13 is a partial enlarged schematic view schematically showing in an enlarged manner a portion where upper and lower phase-shifted disk cutters overlap with each other, and FIG. 14 is a partial enlarged perspective view showing in an enlarged manner the vicinity of a node of a grid which is produced by the phase-shifted disk cutters.

[0152] The components having the same functions as those of the examples shown in FIGS. 1 and 6 are denoted by the identical reference numerals. In the same manner as FIG. 2 and the like, FIGS. 7, 9, 11, and 13 show the upper and lower disk cutters with being vertically separated from each other, and the circumferential faces are shown with being developed to a horizontal plane. In the same manner as FIG. 1 and the like, actually, FIGS. 8, 10, 12, and 14 show a grid which has been developed.

[0153] In the same manner as the first to third examples, also in the examples (FIGS. 7 to 14) of the embodiment, a grid for a plate of a storage battery will be described, and also a method of producing the grid from the lead sheet 2 by the upper and lower disk cutters 1, 1 of the rotary expander will be described. In the fourth example of the embodiment, as shown in FIG. 7, the length Lw of the valleys 1 b is longer than the width Ln of the grooves 1 c. In FIG. 7, particularly, the disk cutter 1 is used in which each of the grooves 1 c is opened at the width Ln and only in the center area of the whole length Lw of a flat face 1 b (Ln<Lw). In FIG. 7, the phases of the upper and lower disk cutters 1, 1 coincide with each other.

[0154] When the metal sheet 2 is passed between the upper and lower disk cutters 1, 1, the node 2 c the length of which is equal to the width Ln of the grooves 1 c is formed, because the upper and lower grooves 1 c, 1 c coincide and overlap with each other. In the four wires 2 b connected to the node 2 c, their ends are pressed by the valley 1 b where the groove 1 c is not opened. As shown in FIG. 8, therefore, the wires are upward or downward bent at the tip ends of the drawn-out portions 2 d which are frontward and backward drawn out from the node 2 c in the longitudinal direction of the lead sheet 2.

[0155] When the grid is stretched in the width direction of the metal sheet 2 to be developed, the tensile stress applied to the four wires 2 b which are drawn out and bent from the node 2 c via the drawn-out portions 2 d is dispersed to the whole drawn-out portions 2 d, so that, even after the developing process, the drawn-out portions 2 d can maintain the state where the portions are drawn out in a substantially longitudinal direction. In all the basal ends where the four wires 2 b are connected to the node 2, therefore, large distortion or rupture does not occur during the developing process, so that corrosion due to electrolyte hardly occurs. As a result, the possibility that a crack of corrosion occurs in the wires 2 b during use of the storage battery can be remarkably reduced.

[0156] In the fourth example of the embodiment, the case where the groove 1 c is opened in the center of the valley 1 b has been described. In the fifth example, the groove 1 c is opened with being shifted to one end of the valley 1 b as shown in FIG. 9. In this case also, the upper and lower grooves 1 c, 1 c coincide and overlap with each other, and hence the node 2 c the length of which is equal to the width Ln of the grooves 1 c is formed. As shown in FIG. 10, however, in one side of each node 2 c in the width direction of the metal sheet 2, two wires 2 b (the right ones in the figure) which are vertically pressed by the ridges 1 a which protrude immediately from the ends of the valleys 1 b where the groove 1 c is opened are vertically bent with starting immediately from the basal end of the node 2 c, and by contrast two wires (the left ones in the figure) which are vertically pressed by the ends of the valleys 1 b where the groove 1 c is not opened are vertically bent at the tip ends of the drawn-out portions 2 d which are rearward drawn out from the node 2 c in the longitudinal direction of the metal sheet 2. The tensile stress applied to the two wires 2 b during the developing process is dispersed to the whole drawn-out portions 2 d, whereby the possibility that a crack of corrosion due to electrolyte occurs in the wires 2 b during use of the storage battery can be reduced.

[0157] As shown in FIG. 11, the grooves 1 c which are opened with being shifted to ends of the valleys 1 b may be formed respectively in the ends which are on the opposite sides along the frontward and backward directions in the upper and lower disk cutters 1. The upper and lower disk cutters 1 are oppositely rotated. In the case of the disk cutters 1 shown in FIG. 9, therefore, disk cutters having different shapes are used as the upper and lower disk cutters. By contrast, in the case of FIG. 11, disk cutters having the same shape can be used as the upper and lower disk cutters, and hence sharing of the parts can be attained. In this case, the upper and lower grooves 1 c, 1 c are shifted from each other, and hence the node 2 c is formed only by the portion where the grooves overlap with each other. As shown in FIG. 12, all of the four wires 2 b connected to the node 2 c are vertically pressed by the valleys 1 b where the groove 1 c is opened, and the valleys 1 b where the groove 1 c is not opened, and hence vertically bent at the tip ends of the drawn-out portions 2 d which are frontward and backward drawn out from the node 2 c in the longitudinal direction of the metal sheet 2. The tensile stress applied to the four wires 2 b during the developing process is dispersed to the whole drawn-out portions 2 d, whereby the possibility that a crack of corrosion due to electrolyte occurs in the wires 2 b during use of the storage battery can be remarkably reduced.

[0158] As shown in FIG. 13, the grooves 1 c which are opened with being shifted to ends of the valleys 1 b may be formed respectively in the ends which are on the opposite sides along the frontward and backward directions in the upper and lower disk cutters 1, and may be shifted in phase so that the upper and lower grooves 1 c, 1 c coincide and overlap with each other. In this case also, the upper and lower valleys 1 b, 1 b are shifted from each other, but the upper and lower grooves 1 c, 1 c coincide and overlap with each other, so that the node 2 c the length of which is equal to the width Ln of the grooves 1 c is formed. As shown in FIG. 14, among the four wires 2 b connected to the node 2 c, the two diagonal wires 2 b (the left rear and right front ones in the figure) are pressed by the upper and lower protrusions 1 a to be vertically bent with starting immediately from the basal end of the node 2 c, but the remaining two wires 2 b (the left front and right rear ones in the figure) which are vertically pressed by the ends of the valleys 1 b where the groove 2 c is not opened are vertically bent at the tip ends of the drawn-out portions 2 d which are drawn out from the basal end of the node 2 c in the longitudinal direction of the metal sheet 2. The tensile stress applied to the two wires 2 b during the developing process is dispersed to the whole drawn-out portions 2 d, whereby the possibility that a crack of corrosion due to electrolyte occurs in the wires 2 b during use of the storage battery can be reduced.

[0159] In the first to sixth examples, the various combinations in which the phases of the upper and lower disk cutters 1, 1 are shifted from each other, the upper and lower flat faces 1 b, 1 b have different lengths, or the length of the valleys 1 b of the disk cutters 1 is longer than the width of the grooves 1 c have been described. Any other combinations of the disk cutters 1, 1 can be used as far as at least one of the wires 2 b connected to the node 2 c has a shape in which it is bent via the drawn-out portion 2 d. For example, the upper and lower valleys 1 b, 1 b may have different lengths, and the width of both or one of the upper and lower grooves 1 c may be shorter than the lengths of the valleys 1 b. In addition to this, the phases of the upper and lower disk cutters 1, 1 may be shifted from each other.

[0160] In the first to sixth examples, in order to simplify the description, the case where the grid is produced by passing the metal sheet 2 of lead or a lead alloy between the upper and lower disk cutters 1, 1 has been described. The manner of arranging disk cutter rolls in which such disk cutters 1 are combinedly used can be arbitrarily selected, and is not restricted to the case where the metal sheet 2 is passed through two opposed disk cutter rolls. The grid may be produced with arranging three or more disk cutter rolls in the transportation path of the metal sheet 2.

[0161] In the first to sixth examples, the case where the metal sheet 2 of lead or a lead alloy is processed to produce a grid for a battery plate has been described. The invention can be similarly applied also to the case where the metal sheet 2 of a metal other than lead or a lead alloy is processed to produce another grid for a battery plate.

[0162] As apparent from the above description, according to the grid for a battery plate of the invention, a wire is bent at the tip end of a drawn-out portion which is drawn out in a substantially straight manner from a node, and hence the wire can be prevented from being easily corroded to cause a crack of corrosion.

[0163] According to the method of producing a grid for a battery plate of the invention, a wire is bent at the tip end of a drawn-out portion which is drawn out in a substantially straight manner from a node, whereby wires of a produced grid can be prevented from being easily corroded.

[0164] Embodiment (2) of the Invention

[0165] Next, a second embodiment of the invention will be described with reference to the accompanying drawings.

[0166] FIGS. 15 to 17 show the second embodiment of the invention. FIG. 15 is a partial enlarged front view showing a gap face of a disk cutter, FIG. 16 is a partial enlarged front longitudinal section view showing a fence-like portion between slits protruding in a ridge-like shape in a metal sheet, and FIG. 17 is a partial enlarged front view showing a case where, in place of a small slope, a curved faces is interposed in both sides of a valley of a disk cutter.

[0167] In a manner similar to the prior art example shown in FIGS. 37 to 50, also the embodiment of the invention relates to the disk cutter 1 of a rotary expander. The disk cutter 1 is a cutting tool in which a large number of ridges 1 a protrude from the peripheral side face of a thin disk-like steel plate. The ridges 1 a protrude at equal angular intervals from the peripheral side face of the disk cutter 1, and are arranged with forming a constant gap between adjacent ridges. In the same manner as in the prior art example shown in FIG. 41, each of the ridges 1 a is formed so as to protrude in a ridge-like shape from the circumferential face A, and the apex 1 i (see FIG. 41) of the ridge 1 a is rounded so as to smoothly connect the peripheral side faces between the slopes across the apex. In each of the ridges 1 a, the apex is formed with being shifted toward the front side in the rotational direction. As described in the prior art example, with respect to the angles at which the slopes on both the sides of the apex protrude from the circumferential face A, therefore, the front angle θ₁₀ is closer to a right angle or steeper than the rear angle θ₂₀.

[0168] The valley 1 b which elongates along the circumferential face A of the disk cutter 1 is formed between the ridges 1 a. As shown in FIG. 15 in which the circumferential face A that is within the same radius from the axis of the disk cutter is developed to a plane, therefore, the angle formed by the valley 1 b and the front slope of the ridge 1 a that is rearward adjacent thereto is θ₁₀, and the angle formed by the valley and the rear slope of the ridge 1 a that is forward adjacent thereto is θ₂₀. In FIG. 15, since the circumferential face A is shown with being developed to a plane, also the valley 1 b is shown in the same plane as the circumferential face A. Small slopes 1 e are interposed respectively between the valley 1 b and the slopes of the ridges 1 a that are adjacent thereto on both the sides. Each of the small slopes 1 e is a plane which connects the peripheral side face between the valley 1 b and the slope of the ridge 1 a, and has an inclination angle at which the small slope is raised from the valley 1 b, and which is a half of the protruding angle (θ₁₀ or θ₂₀) of the slope of the ridge 1 a from the circumferential face A. Therefore, the small slopes 1 e are connected also to the slopes of the ridges 1 a at the same angle as the rising angle from the valley 1 b, and the slopes of the ridges 1 a protrude from the valley 1 b via the small slopes 1 e at the two-step bending angles.

[0169] In the disk cutter 1, the grooves 1 c which are similar to those of the prior art example are formed in both the disk-like faces and in every other valley 1 b. In the same manner as the prior art example shown in FIGS. 38 and 39, a large number of thus configured disk cutters 1 are arranged on a rotation shaft with being separated from each other to form a roll, and two rolls of the disk cutters 1 are vertically arranged.

[0170] In the rotary expander of the second embodiment of the invention, the metal sheet 2 is passed between the upper and lower roll-like disk cutters 1, thereby forming the slits 2 a in the metal sheet 2. In the metal sheet 2, as shown in FIG. 2, the fence-like portion between the slits 2 a is pressed by the ridges 1 a of the upper and lower disk cutters 1 to protrude in a ridge-like shape. At this time, as shown in FIG. 16, small bent portions 2 h which are bent in two steps by the small slopes 1 e are formed between the node 2 c where the slits 2 a are disconnected, and the fence-like portion (the wires 2 b) which protrudes in a ridge-like shape. The small bent portions 2 h are bent at both ends by an angle which is a half of a bending angle (θ₁₁ or θ₂₁) in the prior art.

[0171] In the second embodiment of the invention, therefore, the fence-like portion (the wires 2 b) between the slits 2 a of the metal sheet 2 can be bent in two steps via the small bent portion 2 h by an angle which is a half of the conventional bending angle. When the metal sheet 2 is stretched to widen the slits 2 a to form meshes, therefore, a phenomenon that the degree of cut of the slits 2 a in an end of the fence-like portion is increased to shorten the length of the nodes 2 c shown in FIG. 43 or reduce the strength of the nodes to cause rupture does not occur. As a result, edges of the meshes can be prevented from being easily corroded by electrolyte.

[0172] In the second embodiment of the invention, the case where each of the valleys 1 b is configured by a face which extends along the circumferential face A has been described. Alternatively, the valley 1 b may be configured by a face other than that extending along the circumferential face A, such as a flat face. In the case where the valley 1 b is configured by a face extending along the circumferential face A as in the embodiment or another curved face, the inclination angle of the face is the inclination angle of a contacting face of a portion which is immediately in front of the portion connected to the small slope 1 e.

[0173] In the second embodiment of the invention, the case where the small slope 1 e is formed in both the sides of each of the valleys 1 b has been described. Alternatively, the small slope 1 e may be formed only between each of the valleys 1 b and at least the front slope of the ridge 1 a which is rearward adjacent to the valley in the rotational direction, because the slope of the rear ridge 1 a protrudes at the steeper angle θ₁₀ with respect to the circumferential face A and hence a crack of corrosion in the node 2 c can be effectively prevented from occurring, even in a configuration in which the bending angle of the slope is simply divided into two steps. In the second embodiment of the invention, the case where the small slope 1 e has an intermediate inclination angle between the slopes of the valley 1 b and the ridge 1 a has been described. When the inclination angle is set to an arbitrary angle between the slopes of the valley 1 b and the ridge 1 a, the bending angle can be made gentle. However, the bending angles in both the ends of the small slope 1 e are gentlest in the case where the intermediate inclination angle is employed as in the embodiment.

[0174] In the second embodiment of the invention, the case where the small slope 1 e is interposed between the valley 1 b and the slope of the ridge 1 a has been described. Alternatively, as shown in FIG. 17, a curved face if may be interposed between the valley 1 b and the slope of the ridge 1 a. All contact faces which are in contact with the curved face 1 f must have an inclination angle between an inclination angle of the valley 1 b and that of the slope of the ridge 1 a. Preferably, the curved face 1 f is rounded so that the inclination angle is closer to the inclination angle of the valley 1 b as more approaching the valley 1 b, and closer to that of the slope of the ridge 1 a as more approaching the slope of the ridge 1 a. When the thus configured slope 1 e is interposed between the valley 1 b and the slope of the ridge 1 a, the fence-like portion between the slits 2 a of the metal sheet 2 can smoothly protrude in a ridge-like shape from the node 2 c. Therefore, cracks due to reduced strength caused by formation of angled bends can be prevented from occurring, and edges of meshes can be prevented from being easily corroded by electrolyte.

EXAMPLE 1

[0175] The case where the lead sheet 2 made of lead or a lead alloy is used as the metal sheet 2, and the slits 2 a are formed and developed by using the disk cutter 1 of the prior art example in which the valley 1 b is directly connected to the slope of the ridge 1 a without interposing the small slope 1 e therebetween was compared with that where the slits 2 a are formed in the lead sheet 2 by using the disk cutter 1 of the embodiment in which the small slope 1 e is interposed between the valley 1 b and the slope of the ridge 1 a. Results of the comparison are shown in Table 1. TABLE 1 Development Inclination amount before Life perform- angle of small crack (100 in ance (100 in slope (θ₁₀ = case of no case of no 40°) small slope) small slope) No small slope 100 100 Prior art ex- ample  5° 105 101 Example 10° 109 105 Example 15° 116 113 Example 20° 122 116 Example 30° 116 110 Example

[0176] In Table 1 above, in the case where the inclination angle of the valley 1 b is set to 0° and that of the steep slope of the ridge 1 a which is in rear of the valley 1 b, i.e., the angle θ₁₀ is set to 40°, the prior art example of “no small slope”, and examples in which the inclination angle of the small slope 1 e with respect to the steep slope is set to 5°, 10°, 15°, 20°, or 30° were compared with one another in amount of development which was conducted until crack occurred, and life performance of a lead storage battery. Specifically, the slits 2 a were formed in the lead sheet 2 by using a rotary expander having the disk cutters 1 of each kind, and the amount of development which was conducted until crack occurred in the nodes 2 c was measured. The slits 2 a were formed in the lead sheet 2 by using a rotary expander having the disk cutters 1 of each kind, and developed by a predetermined amount to form a grid, an active material was filled into the grid, and the grid was then cured and dried to form a positive plate. The positive plate was combined with a negative plate which was produced by a conventional method, and a separator which is configured mainly by microporous polyethylene, to produce a lead storage battery for an automobile. The lead storage battery was subjected to a light-load life test according to JIS standard (D 5301) in a gaseous phase of 75° C. After the life test was ended, the battery was disassembled, and the rates of crack portions in the higher- and lower-angle sides of the node 2 c in the grid were investigated.

[0177] From the comparison results shown in Table 1, it has been seen that, in all the cases where the small slope 1 e is interposed, the development amount before the node 2 c cracks is larger than that in the prior art example, and maximized in the case where the small slope 1 e has the inclination angle of 20° which is an intermediate inclination angle between the valley 1 b and the slope of the ridge 1 a, while becoming larger as being nearer to the inclination angle. Furthermore, it has been seen that, in accordance with this, also the SAE life performance at 75° C. is excellent.

[0178] As apparent from the above description, according to the method of producing a grid for a battery plate of the invention and the apparatus for the method, a small slope or a curved face is interposed between each of the valleys and the slope of each of the ridges in the disk cutter, the angled bend between the valley and the slope of the ridge can be set to two steps so as to be gentle, or to be smoothly conducted. Therefore, the rising angle by which the fence-like portion between the slits of the metal sheet protrudes in a ridge-like shape can be made gentle, and the portion can be smoothly raised. Consequently, the portion can be prevented from being easily corroded by electrolyte, thereby preventing the capacity of a battery from being reduced, and the life of the battery from being shortened.

[0179] Embodiment (3) of the Invention

[0180] Next, a third embodiment of the invention will be described with reference to the accompanying drawings.

[0181] The third embodiment corresponds to a modification of the above-described second embodiment, and is also a preferable example of means for solving above discussed Problem (2) to be solved.

[0182]FIGS. 18 and 19 show the third embodiment of the invention. FIG. 18 is a partial enlarged front view showing an inclined valley of a disk cutter, and FIG. 19 is a partial enlarged front longitudinal section view showing a fence-like portion between slits protruding in a ridge-like shape in a metal sheet.

[0183] In a manner similar to the prior art example shown in FIGS. 37 to 50, also the third embodiment of the invention relates to the disk cutter 1 of a rotary expander. The disk cutter 1 is a cutting tool in which a large number of ridges 1 a protrude from the peripheral side face of a thin disk-like steel plate. The ridges 1 a protrude at equal angular intervals from the peripheral side face of the disk cutter 1, and are arranged with forming a constant gap between adjacent ridges. As shown in FIG. 18 in which the circumferential face A that is within the same radius from the axis of the disk cutter is developed to a plane, each of the ridges 1 a is formed so as to protrude in a ridge-like shape from the circumferential face A, and rounded. In each of the ridges 1 a, the apex of the ridge-like shape is formed with being shifted toward the front side in the rotational direction. As described in the prior art example, with respect to the angles at which the slopes on both the sides of the apex protrude from the circumferential face A, therefore, the front angle θ₁₀ is closer to a right angle or steeper than the rear angle θ₂₀ (hereinafter, for each of the ridges 1 a, the side of the front angle θ₁₀ is referred to as “the higher-angle side”, and the side of the rear angle θ₂₀ is referred to as “the lower-angle side”).

[0184] The valley 1 b in which the front side is inclined toward the center with respect to the circumferential face A of the disk cutter 1 is formed between the ridges 1 a. The valley 1 b is configured by a face which is obtained by rotationally displacing the curved face extending along the circumferential face A so as to incline the front side toward the center, about the crossing line between the curved face and the slope of the rear ridge 1 a on the higher-angle side. Therefore, the valleys 1 b is a face in which all contact faces contacting with the valley 1 b are inclined toward the center by a constant angle as being more forward than the contact face which is centered at the rotation axis of the disk cutter 1 and has the same angular position. At this time, it is preferable to set the inclination angle of the valley 1 b to 1° or more. Since FIG. 18 shows the circumferential face A with developing the face to a plane, also the valley 1 b is shown as a plane which is inclined by a constant angle with respect to the circumferential face A. When the valley 1 b is inclined in this way, the bending angle θ₃₀ between the valley and the higher-angle side slope of the ridge 1 a which is rearward adjacent thereto is larger than the angle θ₁₀ with respect to the circumferential face A or becomes gentle. The bending angle θ₄₀ between the valley and the lower-angle side slope of the ridge 1 a which is forward adjacent thereto is smaller than the angle θ₂₀ with respect to the circumferential face A or becomes steep. However, the angle θ₁₀ with respect to the circumferential face A is originally sufficiently closer to a right angle or steeper than the angle θ₂₀, and hence the angle θ₄₀ with respect to the valley 1 b is closer to the angle θ₃₀ so as to reduce the difference.

[0185] In the disk cutter 1, the grooves 1 c which are similar to those of the prior art example are formed in both the disk-like faces and in every other valley 1 b. In the same manner as the prior art example shown in FIGS. 38 and 39, a large number of thus configured disk cutters 1 are arranged on a rotation shaft with being separated from each other to form a roll, and two rolls of the disk cutters 1 are vertically arranged. At this time, the upper and lower rollers of the disk cutters 1 are placed in the same manner as the prior art example shown in FIG. 39. In the embodiment, however, the valley 1 b is inclined, and hence the rolls are placed respectively at levels which allow at least the portions of the faces of the valleys 1 b which are closest to the center to slightly overlap with each other without forming a gap therebetween.

[0186] In the rotary expander of the third embodiment of the invention, the metal sheet 2 is passed between the upper and lower roll-like disk cutters 1, thereby forming the slits 2 a in the metal sheet 2. In the metal sheet 2, as shown in FIG. 19, the fence-like portion between the slits 2 a is pressed by the ridges 1 a of the upper and lower roll-like disk cutters 1 to protrude in a ridge-like shape to be formed as the wires 2 b. At this time, the node 2 c in which the slits 2 a are disconnected is obliquely formed by the valleys 1 b of the disk cutters 1. As a result, the bending angle θ₃₁ with respect to the higher-angle side slope of the rear ridge is made gentle, and the bending angle θ₄₁ with respect to the lower-angle side slope of the front ridge is made steep, so that the difference between the angles is reduced. The fence-like portions (the wires 2 b) between the slits 2 a which are adjacent to each other protrude respectively in opposite directions or upward and downward directions. Therefore, the fence-like portions on both sides of the node 2 c are inclined respectively in opposite directions or upward and downward directions, and hence the node 2 c itself is in a twisted state.

[0187] In the embodiment, therefore, the fence-like portion between the slits 2 a of the metal sheet 2 is prevented from being bent only in the higher-angle side by a steep angle, and the bending angles θ₃₁ and θ₄₁ of the higher- and lower-angle sides can be averaged. When the metal sheet 2 is stretched to widen the slits 2 a to form meshes, therefore, the phenomenon in the prior art that the degree of cut in only the higher-angle side in the fence-like portion between the slits 2 a is large and the length and strength of the node 2 c shown in FIG. 43 are reduced to cause rupture in edge portions does not occur. Consequently, edges of meshes can be prevented from being easily corroded by electrolyte.

[0188] In the embodiment, the case where the valley 1 b is configured by a face which is obtained by rotationally displacing the curved face extending along the circumferential face A has been described. The valley may be configured by any kind of face as far as all contact faces contacting with the valley 1 b are inclined toward the center as being more forward than the contact face which is in contact with the circumferential face A at the same angular position. Alternatively, the face may be a curved or flat face other than a face extending along the circumferential face A. When the valley 1 b is a flat face which is inclined by a small angle, there sometimes arises a case where only a front end portion is more inclined toward the outer periphery as being more forward than the contact face of the circumferential face A at the same angular position. Also in such a case, it is possible to attain the effect that the bending angle with respect to the higher-angle side slope of the rear ridge 1 a is made gentle. In some cases, the portion between the valley 1 b and the lower-angle side slope of the ridge 1 a which is forward adjacent is rounded, or a small slope having an intermediate inclination angle is interposed in the portion. Also in such cases, it is possible to attain not only the effect that the bending angle with respect to the lower-angle side slope of the front ridge 1 a is made further gentle, but also the effect that the bending angle with respect to the higher-angle side slope of the rear ridge 1 a is made gentle. Namely, the face contacting with the valley 1 b may be a face which is inclined toward the center as being more forward than the contact face that is in contact with the circumferential face A at the same angular position, excluding at least a front end portion of the valley 1 b.

[0189] In the embodiment, the case where the valley 1 b is configured so that a face contacting with the valley 1 b is inclined toward the center as being more forward than the contact face which is in contact with the circumferential face A at the same angular position has been described. Alternatively, the face contacting with the valley 1 b may be configured by a face which is more inclined toward the center as being more forward than a plane connecting together cross lines between the circumferential face A and the slopes of the ridges 1 a on both the sides. In the alternative, even when the valley 1 b is a flat face which is inclined by a small angle, a face which is surely inclined over a range to a front end portion is obtained.

EXAMPLE 1

[0190] The case where the lead sheet 2 made of lead or a lead alloy is used as the metal sheet 2, and the slits 2 a are formed and developed by using the disk cutter 1 of the prior art example in which the valley 1 b is not inclined was compared with that where the slits 2 a are formed in the lead sheet 2 by using the disk cutter 1 of the embodiment in which the valley 1 b is inclined. Results of the comparison are shown in Table 2. TABLE 2 Life per- formance (100 in Percentage Percentage case of in- of crack in of crack in clination Inclination lower-angle higher- angle of angle side angle side 0°)  0° 0% 30% 100 Prior art example  1° 0% 25% 105 Example  3° 1% 19% 113 Example  5° 3% 12% 130 Example  8° 5%  6% 152 Example 10° 6%  6% 147 Example

[0191] In Table 2 above, a prior art example in which the inclination angle of the valley 1 b is 0°, and examples in which the inclination angle is 1°, 3°, 5°, 8°, or 10° were compared with each other with respect to the percentages of crack in the higher- and lower-angle sides and life performance of a lead storage battery. Specifically, the lead sheet 2 was formed into a grid by using a rotary expander having the disk cutters 1 of each kind, an active material was filled into the grid, and the grid was then cured and dried to form a positive plate. The positive plate was combined with a negative plate which was produced by a conventional method, and a separator which is configured mainly by microporous polyethylene, to produce a lead storage battery for an automobile. The lead storage battery was subjected to a light-load life test according to JIS standard (D 5301) in a gaseous phase of 75° C. After the life test was ended, the battery was disassembled, and the rates of crack portions in the higher- and lower-angle sides of the node 2 c in the grid were investigated.

[0192] From the comparison results shown in Table 2, it has been seen that, in the prior art example, the percentage of crack in the higher-angle side is high, and by contrast, in the examples, the percentage of crack in the lower-angle side is slightly higher but that in the higher-angle side is greatly reduced as the inclination angle is larger, and the total percentage of crack is lower as the inclination angle is larger. Furthermore, it has been seen that, in accordance with this, also the SAE life performance at 75° C. is more improved as the inclination angle is larger, until the inclination angle has a certain large value.

[0193] As apparent from the above description, according to the method of producing a grid for a battery plate of the invention and the apparatus for the method, the valley between the ridges of the disk cutter is more inclined toward the center as being more forward. Consequently, the bending angle between the valley and the steep slope of the ridge that is rearward adjacent thereto can be made large so as to be gentle. When slits are formed in a metal sheet, therefore, the node is inclined, and the steep rising angle by which the fence-like portion between the slits protrudes in a ridge-like shape can be made gentle, so that the portion can be prevented from being easily corroded by electrolyte, thereby preventing the capacity of a battery from being reduced, and the life of the battery from being shortened.

[0194] Embodiment (4) of the Invention

[0195] Next, a fourth embodiment of the invention will be described with reference to the accompanying drawings.

[0196] FIGS. 20 to 26 show the fourth embodiment of the invention. FIG. 20 is a front view showing the whole of a disk cutter, and a peripheral edge of the disk cutter in an enlarged manner, FIG. 21 is a partial enlarged perspective view showing inclined faces formed in peripheral side faces of ridges which are opposed across a valley of the disk cutter, FIG. 22 is a partial enlarged side longitudinal section view showing a slit forming step of a rotary expander and illustrating a manner in which wires of a metal sheet are twisted with being pressed by the inclined faces formed in ridges of disk cutters of upper and lower disk cutter rolls, FIG. 23 is a partial enlarged perspective view showing a metal sheet and illustrating a node formed in the slit forming step, and four wires connected thereto, FIG. 24 is a partial enlarged perspective view showing another first configuration example of the inclined faces formed in peripheral side faces of ridges which are opposed across a valley of the disk cutter, FIG. 25 is a partial enlarged perspective view showing another second configuration example of the inclined faces formed in peripheral side faces of ridges which are opposed across a valley of the disk cutter, and FIG. 26 is a partial enlarged perspective view showing another third configuration example of the inclined faces formed in peripheral side faces of ridges which are opposed across a valley of the disk cutter.

[0197] In a manner similar to the prior art example, also the fourth embodiment of the invention relates to a rotary expander for producing a grid for a battery (lead storage battery) plate. As shown in FIG. 38, the metal sheet 2 is passed between the upper and lower disk cutter rolls to form a large number of zigzag slits 2 a in the metal sheet 2. The portion between the slits 2 a in the width direction of the lead sheet 2 is configured as the wire 2 b, and that between the slits in the advancing direction is configured as the node 2 c.

[0198] In each of the disk cutter rolls, in the same manner as the prior art example, a large number of the disk cutters 1 are arranged with forming a gap therebetween. However, the disk cutter 1 is configured in a manner different from the prior art example. In the disk cutter 1, as shown in FIG. 20, the ridges 1 a having a relatively long circumferential length, and the valleys 1 b having a relatively short circumferential length are alternately formed in a large number in the peripheral edge of a metal disk over the whole circumference. In each of the valleys 1 b, a peripheral side face configured by a reference circumferential face of a predetermined radius and centered at the axis of the disk cutter 1 is formed in the same manner as the prior art example. The groove 1 c which is opened in a peripheral side face of the valley 1 b is formed in a peripheral edge portion of one of disk faces in which valleys 1 b that are adjacent to each other via the ridge 1 a are formed in an oppositely reverse manner. Also in FIG. 20, the oval enlarged view shows the reference circumferential face in a form developed to a plane.

[0199] In each of the ridges 1 a of the disk cutter 1, a peripheral side face which protrudes in a ridge-like shape from the reference circumferential face toward the outer periphery. As shown in the oval enlarged view of FIG. 20, the peripheral side face of the ridge 1 a is formed in a ridge-like shape in which the peripheral side face obliquely rises in a substantially linear manner from the reference circumferential face that is a peripheral side face of the valley 1 b toward the outer peripheral side, is curved in the apex of the ridge 1 a, and obliquely falls in a substantially linear manner toward the inner peripheral side to return to the reference circumferential face. The rising and falling portions of the peripheral side face of the ridge 1 a are not evenly formed in the rotational direction with respect to the apex of the ridge 1 a. Actually, the apex is shifted toward the front side in the rotational direction, so that the rising portion which is in the front side in the rotational direction is a peripheral side face which is steeper than the falling portion in the rear side. The configuration in which the apex of the ridge 1 a is shifted toward the front side in the rotational direction is identical with that of the prior art.

[0200] Inclined faces 1 g, 1 g are formed in the rising and falling portions of the peripheral side face of the ridge 1 a, respectively. As shown in FIG. 21, the inclined faces 1 g are formed respectively in ranges from middles of the rising and falling portions of the peripheral side faces of the ridges 1 a, to the valley 1 b, and, in the same manner as the grooves 1 c, formed as faces which are alternately inclined in opposite directions for each of the valleys 1 b. For each of the valleys 1 b, the inclined faces are more inclined toward the center of the rotation shaft of the disk cutter 1 as being nearer to the disk face (directed to the right lower side in FIG. 21) in which the groove 1 c opened in the valley 1 b is formed, respectively in the falling portion of the peripheral side face of the ridge 1 a which is in the front side in the rotational direction, and the rising portion of the peripheral side face of the ridge 1 a which is in the rear side in the rotational direction (or in the falling and rising portions which are opposed to each other across the valley 1 b), the ridge portions being adjacent to both the sides of the valley 1 b. In the peripheral side face of a certain one of the ridges 1 a, therefore, the inclined face 1 g formed in the rising portion, and that formed in the falling portion are inclined in opposite directions, respectively.

[0201] In the embodiment, the inclined face 1 g is configured by a plane enclosed by a triangle in which the vertexes are points A, B, and C shown in FIG. 21. In this case, the point A is a point where, when the distance (height) from the intermediate part of the edge of the falling portion of the peripheral side face of the ridge 1 a shown in the right upper side of FIG. 21 on the side of the disk face directed to the right lower side in FIG. 21, i.e., the reference circumferential face that is a peripheral side face of the valley 1 b, to the apex of the ridge 1 a is indicated by H, a tangential line with a circumferential face of a radius which is larger by H/2 than the predetermined radius of the reference circumferential face, and the peripheral side face of the ridge 1 a intersects the disk face. The point B is a point where the edge of the falling portion of the peripheral side face of the ridge 1 a on the side of the disk face directed to the left upper side in FIG. 21 is in contact with the peripheral side face of the valley 1 b. The point C is a point which is on the peripheral edge the disk face directed to the right lower side in FIG. 21, and closer to the ridge 1 a along the reference circumferential face than a point O where the falling portion of the original peripheral side face of the ridge 1 a is in contact with the original peripheral side face of the valley 1 b. Since the point C is closer toward the ridge 1 a, the inclined face 1 g is inclined with respect to the falling portion of the peripheral side face of the ridge 1 a.

[0202] In the above, the inclined face 1 g formed in the right upper side of the valley 1 b shown in FIG. 21 has been described. Also the inclined face 1 g formed in the left lower side of the valley 1 b shown in FIG. 21 is configured by a plane enclosed by a similar triangle, and is a face which is inclined in the same direction with respect to the peripheral side face of the ridge 1 a. For another valley 1 b which is adjacent to the valley 1 b through the ridge 1 a, and which is not shown in FIG. 21, inclined faces 1 g, 1 g which are inclined in opposite directions are formed.

[0203] When the metal sheet 2 is passed between disk cutter rolls using the disk cutters 1 in which the inclined faces 1 g are formed, the metal sheet is vertically pressed by the inclined faces 1 g of the ridges 1 a of the disk cutters 1 as shown in FIG. 22, at the timing when the slits 2 a are formed by the ridges 1 a, whereby the wires 2 b are deformed in a ridge-like shape while being twisted. The section shape is not a rectangular shape but a parallelogram shape. In each of the wires 2 b, as shown in FIG. 23, the portion which is pressed by the inclined face 1 g of the ridge 1 a, i.e., the end portion connected to the node 2 c (the dotted portion in FIG. 23) is formed with being twisted from the beginning. The twisting direction of the end portion of the wire 2 b indicated by the arrow R of FIG. 23 is opposite to the direction in which the node 2 c connected to the end portion is twisted during the developing process, i.e., the direction of the arrow F which has been described in conjunction with FIG. 45. The relationship in which the twisting directions of the arrows R and F are opposite to each other is applied also to the two upper wires 2 b shown in FIG. 23. In the node 2 c which is twisted in the direction of the arrow G in FIG. 45 during the developing process, the wires 2 b connected to the node are formed with being twisted in the direction opposite to that of the arrow G.

[0204] According to the configuration, when the slits 2 a are formed in the metal sheet 2, the rotary expander of the embodiment deforms the wires 2 b into a ridge-like shape in a state where the end portions of each of the wires 2 b are pretwisted by the inclined faces 1 g formed in the peripheral side faces of the ridges 1 a of the disk cutter 1. Moreover, the end portions of the wire 2 b are twisted in the direction opposite to the direction in which the node 2 c is twisted during the process of developing the metal sheet 2. Even when the node 2 c is twisted during the developing process in which the metal sheet 2 is actually developed, therefore, the wires 2 b connected to the node receive torsion stress in which the previously applied twisting is canceled. In the wires 2 b, consequently, influence of torsion stress applied to the end portions can be reduced, and the torsion stress can be prevented from being concentrated into the vicinity of the apex 2 e of the wire 2 b.

[0205] In the embodiment, the case where the point C of the inclined face 1 g is made closer to the ridge 1 a along the reference circumferential face than the point O as shown in FIG. 21 has been described. Alternatively, as shown in FIG. 24, the point C may be made close toward the axis along the edge of the groove 1 c, i.e., a radial direction of the disk cutter 1. In the case of FIG. 21, the peripheral side face of the valley 1 b is widened by the area of the triangle BOC. When the inclined faces are configured as shown in FIG. 24, the inclined faces 1 g are naturally connected to the peripheral side face of the valley 1 b and the groove 1 c, so that twisting applied to the end portions of the wire 2 b can be smoothed. In the case of FIG. 24, however, the peripheral side face of the valley 1 b is caused to extend along the side BC of the inclined face 1 g by forming a tapered face in which the edge on the side of the disk face where the groove 1 c is not formed coincides with the reference circumferential face and the radius is made smaller as being nearer toward the disk face where the groove 1 c is formed.

[0206] Alternatively, as shown in FIG. 25, the point B of the inclined face 1 g in FIG. 24 may be moved to the edge of the opening of the groove 1 c along the reference circumferential face. In the alternative, although even the maximum width of the inclined face 1 g is only about one half of the width of the peripheral side face of the ridge 1 a, the torsion stress can be reduced even in the case where about a half portion of the width of the wire 2 b is pretwisted instead of the whole width.

[0207] Since the groove 1 c for forming the node 2 c in the metal sheet 2 is used for preventing the slits 2 a from being formed in the metal sheet 2, by means of the gap between the groove and the groove 1 c of the opposed disk cutter 1, the groove 1 c is not always required to be rectangular. As shown in FIG. 26, for example, the groove 1 c may be formed by chamfering the peripheral side face of the valley 1 b, so as to be configured by a face through which edge sides of the inclined faces 1 g on both sides are connected to each other.

[0208] The peripheral side faces of the ridges 1 a of the disk cutters 1 which are alternately opposed are pressed to each other through the metal sheet 2, thereby forming the slits 2 a in the metal sheet 2. Therefore, it is preferable to set the angle of the edge formed by the peripheral side face of the ridge 1 a and the corresponding one of the disk faces of the disk cutters 1, to be as acute as possible, and usually to 90°. When the inclined face 1 g is formed in the peripheral side face of the ridge 1 a, however, the edge between the inclined face 1 g and the disk face inevitably has an obtuse angle. When the angle is excessively large, the metal sheet 2 cannot be surely cut and the slits 2 a are not formed. Therefore, the inclination angle of the inclined face 1 g must be set so as not to be excessively large. Preferably, the inclination angle with respect to the reference circumferential face is set to be equal to or smaller than 40°, so that the angle of an edge between the inclined face and the disk face can be set to 60° or more, thereby enabling the slits 2 a to be surely formed in the metal sheet 2.

[0209] In order to prevent torsion stress from being concentrated into the vicinity of the apex 2 e of the wire 2 b, preferably, the inclined face 1 g is formed with starting from a position which is as near as possible to the apex of the ridge 1 a. Therefore, it is preferable to set the point A of the inclined face 1 g which is nearest to the apex to a level that is at least one third of the height H of the apex. In the embodiment, the point A is located at a level that is about a half of the height H of the apex. It is a matter of course that the inclined face 1 g may be formed with starting from a position which is nearer to the apex. When the inclined face 1 g is formed so as to extend to a position which is very near to the apex of the ridge 1 a, however, the inclined face 1 g abuts against the metal sheet 2 at the timing when cutting for the slits 2 a is initially formed in the metal sheet, and hence the edge with respect to the disk face has an obtuse angle, thereby causing the possibility that the cutting operation cannot be smoothly started.

[0210] In the embodiment, the case where the inclined face 1 g is formed as a flat face has been described. However, the inclined face is not always necessary to be flat, as far as the face more approaches the axis of the disk cutter 1 as being nearer to the disk face on the side where the groove 1 c of the adjacent valley 1 b is formed, and may be formed by a curved face or a plurality of flat faces. The inclined face 1 g is not required to be a triangle surrounded by three vertexes.

[0211] In the embodiment, the rotary expander in which the metal sheet 2 is passed between upper and lower or two disk cutter rolls has been described. The disk cutter rolls can be arranged in an arbitrary manner. The invention can be similarly applied also to a rotary expander in which the metal sheet 2 is passed between three or more disk cutter rolls that are opposedly arranged.

[0212] In the embodiment, the case where the metal sheet 2 is processed to produce a grid which is to be used in a battery plate of a lead storage battery has been described. The invention is not restricted to a lead storage battery, and can be applied also to a battery of any kind as far as a similar grid is used as a current collecting member of a battery plate. A grid can be produced by using a metal sheet of an appropriate material which corresponds to the kind of the battery.

EXAMPLE 3

[0213] The grids of the embodiment and the prior art example were produced from the metal sheets (lead sheet) 2 by using the disk cutter 1 which has been described in the embodiment, and the disk cutter 1 which has been described in the prior art example. The rate of rupture was investigated by observing in detail the vicinities of apexes 2 e of the wires 2 b after development. An active material was filled into the grids of the embodiment and the prior art example, and the grids were then cured and dried to form positive plates. The plates were incorporated into lead storage batteries (Type 55D23 of JIS) for an automobile, and a given amount of diluted sulfuric acid of a predetermined specific gravity was poured and formation was performed to complete the batteries. An overcharge test according to JIS was conducted to test the life performance, and the breakage rate of the wires 2 b after the test was investigated. In all the lead storage batteries, a conventional plate was used as the negative plate, and a separator which is configured mainly by microporous polyethylene was interposed between the plates.

[0214] In the ridge 1 a of the disk cutter 1 of the embodiment, the inclined face 1 g was configured as a triangular flat face such as shown in FIG. 21. Grids in which the height from reference circumferential face that is a peripheral side face of the valley 1 b to the inclination starting position (point A) of the inclined face 1 g which is nearest to the apex is 20%, 50% (H/2), or 70% of the height H of the apex of the ridge 1 a were produced. In principle, the inclination angle of the inclined face 1 g with respect to the reference circumferential face was set to 30°. In grids in which the inclination starting position of the inclined face 1 g is set to 70%, however, a plurality of grids were produced in a range of 10°to 50°.

[0215] Results of comparisons between the embodiment and the prior art example are shown in Table 3. In the specimen which is shown in the last row of Table 3, and in which the inclination angle of the inclined face 1 g is set to 50°, a grid could not be produced, and hence it was impossible to check and test the specimen, because the edge between the inclined face 1 g and the disk face of the disk cutter 1 was so obtuse that the metal sheet 2 could not be cut and the slits 2 a were not formed. From this, it has been seen that it is preferable to set the inclination angle of the inclined face 1 g to 40° or less. TABLE 3 Rate of Life per- Inclina- rupture formance Breakage tion Angle of in vicin- (prior rate of starting inclined ity of art = wires af- position face apex 100) ter test Remarks None None 40 100 40 Prior art example 20% 30° 30 115 30 Example 50% 30° 15 130 15 Example 70% 30° 5 140 0 Example 70% 10° 24 118 25 Example 70% 20° 15 129 12 Example 70% 40° 5 115 0 Example 70% 50° — — —

[0216] As a result of the comparison, it has been confirmed that the rate of rupture in the vicinity of the apex 2 e in all the examples is lower than that of the prior art example or 40% and all the examples are effective in suppression of occurrence of rupture. In all the examples, with respect to the life performance and the breakage rates of the wires 2 b after test, the life was longer and the breakage rate was lower than those of the prior art example in accordance with the reduction of the rate of rupture. In the specimen in which the inclination starting position of the inclined face 1 g was set to 20%, the difference with respect to the prior art example is relatively small, and hence it has been seen that it is preferable to set the inclination starting position to a position which is at least one third (about 33%) or higher of the height H of the apex of the ridge 1 a.

[0217] As apparent from the above description, according to the grid for a battery plate of the invention and the apparatus for the grid, the wires of the metal sheet are pressed into a ridge-like shape in a twisted state by the inclined faces formed in the peripheral side faces of the ridges of the disk cutter. Therefore, concentration of torsion stress of the opposite direction in the vicinity of the apexes of the wires and generated during the developing process can be suppressed. As a result, corrosion and a crack of corrosion can be prevented from occurring in the wires of the grid, so that a failure of a battery can be suppressed from occurring and the life of a battery can be prolonged.

[0218] Embodiment (5) of the Invention

[0219] FIGS. 27 to 29 show a fifth embodiment of the invention. FIG. 27 is a longitudinal section view showing a first example of formation of a node in the metal sheet 2 by a disk cutter, FIG. 28 is a longitudinal section view showing a second example of formation of a node in the metal sheet 2 by a disk cutter, and FIG. 29 is a longitudinal section view showing a third example of formation of a node in the metal sheet 2 by a disk cutter.

[0220] As shown in FIG. 27(a), two disk cutter rolls each configured by a large number of such disk cutters 1 are vertically arranged, and a lead sheet 2 is passed between the rolls, thereby forming slits 2 a and the nodes 2 a. At this time, the upper and lower disk cutter rolls are placed respectively at levels which allow the valleys 1 b of the upper and lower disk cutters 1 to slightly overlap with each other. In at least both disk faces of the peripheral side face of the disk cutter 1 which is not a ridge 1 a, as shown in FIG. 27(b), a chamfered portion 1 m is formed so as to be lowered toward each of the grooves 1 c which are alternately disposed in the width direction. In the disk cutter 1, specifically, the ridges 1 a, and the valley 1 b between the ridges 1 a are formed, and the chamfered portion 1 m is disposed over a range from the peripheral side face of the valley 1 b to the groove 1 c. The chamfered portion 1 m is lowered as moving from the peripheral side face of the valley 1 b toward the groove 1 c. A new ridgeline 1 j which is formed on the side of the groove 1 c does not damage the node 2 c of the metal sheet 2.

[0221] As shown in FIG. 28(a) and FIG. 28(b) which is a perspective view showing the vicinity of the valley 1 b of the disk cutter 1, the chamfered portion 1 m which is formed from the peripheral side face of the valley 1 b of the disk cutter 1 to the groove 1 c may be further chamfered to form a chamfered portion 1 n in the ridgeline 1 j between the chamfered portion 1 m to the groove 1 c. Alternatively, as shown in FIGS. 29(a) and 29(b), a curved face 1 p may be disposed in the peripheral side face of the valley 1 b. The chamfered portions 1 m and 1 n, or the curved face 1 p is effective in improvement of the strength and suppression of local corrosion which are due to suppression of rupture of the node 2 c formed in the metal sheet 2.

[0222] In the outermost peripheral side face where the groove 1 c is disposed, a certain inclination with respect to the surface of the metal sheet 2 which is being passed between the rolls is provided to the peripheral side face, so that a peripheral side face which is substantially parallel to the metal sheet 2 is eliminated. As apparent from comparison between FIG. 46, and FIGS. 27 to 29, in the conventional method shown in FIG. 46, excessive stress is applied to the bent portions of the node 2 c of the metal sheet 2, and, when the disk cutter 1 of the invention shown in FIGS. 27 to 29 is used, reduced stress is applied to the node 2 c of the metal sheet 2. When the disk cutter 1 of the invention is used, therefore, the strength of the node 2 c can be improved and local corrosion can be suppressed irrespective of the shapes of the other portions of the disk cutter 1.

EXAMPLE 4

[0223] Next, a method of producing an expand grid will be described.

[0224] A plurality of slits which are parallel to one another were formed intermittently and in a zigzag pattern along the longitudinal direction of a lead sheet 2 that is the metal sheet 2. Thereafter, the sheet was developed in the width direction to attain a predetermined dimension to form meshes, thereby producing a grid for a battery plate (see, for example, FIG. 38). An active material was filled into grids which were produced by this method, and the grids were then cured and dried to form positive plates. The positive plates, negative plates which were formed by a usual method, and separators which are configured mainly by microporous polyethylene were combined to one another to produce lead storage batteries (Type 55D23) for an automobile. Then, a given amount of diluted sulfuric acid of a predetermined specific gravity was poured into the batteries, and formation was performed to complete the batteries.

[0225] Batteries having grids that were produced by using the disk cutters 1 in which the angle θ (FIG. 4) formed by the peripheral side face not constituting the ridge 1 a and the disk face 3 is changed in a range of 90 to 60°, and those having grids that were produced by using the disk cutters 1 in which the portion between the peripheral side face and the disk face 3 where the groove 4 is formed is chamfered and various kinds of flat or curved faces are formed were subjected to a light-load life test according to JIS standard (D 5301) in a gaseous phase of 75° C. After the life test was ended, the batteries were disassembled, and the rate of crack of corrosion due to rupture in the node 2 c was investigated (Table 4). TABLE 4 Percent- Life per- age of formance Section crack in (100 in No. view Angle θ node (%) No. 1) Remarks 1 90 5.0 100 Prior art example 2 85 4.6 105 Example 3 75 3.2 113 Example 4 65 2.8 122 Example 5 60 2.8 123 Example 6 75 2.2 135 Example 7 75 2.1 143 Example

[0226] From the results shown in Table 4, is has been seen that, in expand grids produced by using the disk cutter according to the invention, the percentage of crack in nodes is suppressed as compared with the prior art example or No. 1 in which the flat portion forms an angle of 90°. Furthermore, it has been seen that, in accordance with this, also the SAE life performance at 75° C. is improved by forming an angle.

[0227] Embodiment (6) of the Invention

[0228] Hereinafter, a sixth embodiment of the invention will be described with reference to the accompanying drawings.

[0229] FIGS. 30 to 36 show the sixth embodiment of the invention. FIG. 30 is a partial enlarged front longitudinal section view showing a process of forming slits in a metal sheet (including a lead sheet) by disk cutters of upper and lower disk cutter rolls, FIG. 31 is a side view showing the configuration of an endmost disk cutter, FIG. 32 is a partial enlarged perspective view showing the configuration of the endmost disk cutter, FIG. 33 is a partial enlarged perspective view showing the vicinity of an endmost node in a grid which is obtained by developing slits formed in a metal sheet, FIG. 34 is a partial enlarged front longitudinal section view showing a process of forming slits in a metal sheet by using an endmost disk cutter in which inclined faces are formed in peripheral side faces of ridges, FIG. 35 is a partial enlarged front longitudinal section view showing a process of forming slits in a metal sheet by using an endmost disk cutter in which peripheral side faces of valleys are configured as a circumferential face, and FIG. 36 is a partial enlarged front longitudinal section view showing a process of forming slits in a metal sheet by using an endmost disk cutter in which peripheral side faces of valleys are recessed.

[0230] In a manner similar to the prior art example, also the embodiment relates to a rotary expander for producing a grid for a battery plate of a lead storage battery. In the rotary expander, as shown in FIG. 38, the metal sheet 2 is passed between the upper and lower disk cutter rolls to form zigzag slits 2 a in the metal sheet 2. The upper disk cutter roll is configured in the same manner as the prior art example. The lower disk cutter roll has the same configuration as the prior art in which the endmost disk cutters 4 are disposed at both the ends of a large number of the disk cutters 1, but the configuration of the endmost disk cutters 4 is different from that of the prior art example.

[0231] In the same manner as the prior art example, also in each of the endmost disk cutters 4 in the embodiment, as shown in FIGS. 31 and 32, the ridges 4 a and the valleys 4 b are alternately arranged in the peripheral edge. However, the ridges 4 a and the valleys 4 b in the endmost disk cutter 4 show the peripheral edge corresponding to the ridges 1 a and the valleys 1 b in the disk cutter 1 placed in the same disk cutter roll, and do not always have a ridge-like shape or a valley-like shape. Specifically, a peripheral side face configured by a reference circumferential face of a predetermined radius and centered at the axis of the endmost disk cutter 4 is formed in the ridge 4 a, and the valley 4 b is not formed as a concave portion between the ridges 4 a. Unlike the prior art example, the groove 4 c is not formed in each of the valleys 4 b, an inward inclined face 4 d which is a peripheral side face recessed toward the center from the reference circumferential face, and which is inward inclined is formed in each of the valleys 4 b (endmost node forming valleys) on one side which are alternately arranged, and an outward inclined face 4 e which is outward inclined is formed in each of the valleys 4 b on the other side. The peripheral side face of the valley 4 b on the one side forms the inward inclined face 4 d configured by a part of a tapered face wherein the portion contacting with the outer disk face (the rear face in FIG. 31, and the right front face in FIG. 32) of the endmost disk cutter 4 coincides with a circumferential face which is centered at the axis of the endmost disk cutter 4, and in which the radius is smaller than the predetermined radius of the reference circumferential face by 50% of the thickness of the metal sheet 2. The radius of the tapered face is smaller as further moving from the portion toward the inner disk face (the front face in FIG. 31, and the left rear face in FIG. 32). In the valley 4 b on the one side, a peripheral side face that is recessed by one step from the ridges 4 a which are adjacent on both the sides, and in which a peripheral side face is configured by the reference circumferential face is formed, and the peripheral side face is configured by the inward inclined face 4 d which is more inclined toward the center as being nearer the inner disk face of the endmost disk cutter 4. The inward inclined face 4 d is not always required to be a part of a tapered face, and may be a flat face or a curved face of another kind depending on the circumstances of the process or the like, as far as the face is recessed from the peripheral side face of the ridge 4 a and inward inclined.

[0232] Each of the valleys 4 b (the valleys other than the endmost node forming valleys) on the other side of the endmost disk cutter 4 forms the outward inclined face 4 e configured by a part of a tapered face wherein the portion contacting with the inner disk face of the endmost disk cutter 4 coincides with the reference circumferential face of the predetermined radius, and in which the radius is smaller than the predetermined radius as further moving from the portion toward the outer disk face of the endmost disk cutter 4. Therefore, the valley 4 b on the other side has a shape where the outermost diameter is equal to that of the ridges 4 a which are adjacent on both the sides, and in which a peripheral side face configured by the reference circumferential face is formed, and the outward inclined face 4 e is formed by obliquely cutting away in the outer disk face. Also the outward inclined face 4 e is not always required to be a part of a tapered face, and may be a flat face or a curved face of another kind depending on the circumstances of the process or the like, as far as the face is more inclined toward the center than the peripheral side face of the predetermined radius as being nearer to the outer disk face.

[0233] The thus configured endmost disk cutters 4 are placed at the ends of the lower disk cutter roll so as to be outward juxtaposed with the usual disk cutters 1 at the ends of the upper disk cutter roll, respectively. The phase in the rotational direction is adjusted so that the valley 4 b which is an endmost node forming valley of the endmost disk cutter 4 is opposed at the upper end via the metal sheet 2 to the valley 1 b of the disk cutter 1 of the upper disk cutter roll in which the groove 1 c is formed in the opposed face. The metal sheet 2 is transported so as to be passed between the upper and lower disk cutter rolls. At this time, conventionally, the metal sheet 2 is transported with being placed on the transportation face which coincides with the cutting plane S between the upper and lower disk cutter rolls. By contrast, in the embodiment, the transportation face is set to be lower than the cutting plane S by 50% of the thickness of the metal sheet 2. Conventionally, the cutting plane S of the upper and lower disk cutter rolls is set so as to coincide with the transportation face for the metal sheet 2, i.e., the lower face of the metal sheet 2. By contrast, in the embodiment, the cutting plane S of the upper and lower disk cutter rolls is set so as to coincide with the middle portion of the thickness of the metal sheet 2 transported on the transportation face. The cutting plane S is a plane in which the distances from the axes of the upper and lower disk cutter rolls are equal to each other. The predetermined radius of the reference circumferential face constituting the peripheral side face of the valley 1 b of each of the upper and lower disk cutters 1 is slightly larger than the distance from the axis to the cutting plane S. When the peripheral side face of the valley 1 b of the upper disk cutter 1 is at the lower end, the peripheral side face slightly downward exceeds the cutting plane S, and the peripheral side face of the valley 1 b of the lower disk cutter 1, that of the ridge 4 a of the endmost disk cutter 4, and the outermost peripheral end of the peripheral side face of the valleys 4 b of the endmost disk cutter 4 other than the endmost node forming valleys slightly upward exceed the cutting plane S.

[0234] When the metal sheet 2 is passed between the upper and lower disk cutter rolls, in the case where the valleys 1 b of the upper and lower disk cutters 1 overlap with each other in the cutting plane S, as shown in FIGS. 30(a) and 30(c), in the portions of the upper and lower adjacent disk cutters 1 where the grooves 1 c face each other in opposite directions, the metal sheet 2 is cut so that the slits 2 a are formed, and, in the portions where the grooves 1 c face each other, the metal sheet 2 is not cut and the nodes 2 c are formed. In the case where the valley 4 b of the endmost disk cutter 4 is an endmost node forming valley, i.e., the valley faces the groove 1 c of the adjacent upper disk cutter 1 (the left end in FIG. 30(a), and the right end in FIG. 30(c)), the endmost node 2 f connected to the frame portion 2 g of the metal sheet 2 is formed. In the endmost node 2 f, one end in the width direction of the metal sheet 2 (the left one in FIG. 30(a), and the right one in FIG. 30(c)) is directly connected to the frame portion 2 g, and the other end is cut by the valley 1 b of the extreme end disk cutter 1 in the upper disk cutter roll, and also by the valley 1 b of the extreme end disk cutter 1 in the lower disk cutter roll excluding the endmost disk cutter 4. The other end is pressed substantially to the cutting plane S by the valley 1 b of the upper disk cutter 1. In the metal sheet 2 which is transported on the transportation face, therefore, the other end of the endmost node 2 f is deformed with being downward pressed by 50% of the sheet thickness. By contrast, in the same manner as the prior art, in the usual node 2 c, the one and other ends are vertically pressed while exceeding the same cutting plane S, and hence deformation of upward and downward directions and 100% or more of the sheet thickness occurs. In the endmost nodes 2 f, moreover, the portion which is above the valley 4 b of the endmost disk cutter 4 is gently bent from the transportation face along the inward inclined face 4 d, and hence the other end is further gently deformed.

[0235] In the case where the valley 4 b of the endmost disk cutter 4 is not an endmost node forming valley, i.e., the valley faces the groove 1 c of the valley 1 b of the adjacent upper disk cutter 1 (the right end in FIG. 30(a), and the left end in FIG. 30(c)), the end of the frame portion 2 g of the metal sheet 2 is cut by means of the valley 1 b of the extreme end disk cutter 1 in the upper disk cutter roll. In the end of the frame portion 2 g, moreover, the portion which is above the valley 4 b of the endmost disk cutter 4 is gently bent from the transportation face along the outward inclined face 4 e.

[0236] In the case where the ridges 1 a of the upper and lower disk cutters 1 overlap with each other, as shown in FIG. 30(b), the metal sheet 2 is cut by the adjacent upper and lower disk cutters 1 to form the slits 2 a, and the wires 2 b between the slits 2 a are vertically pressed by the ridges 1 a of the disk cutters 1. In the same manner as the prior art, the wires 2 b are pressed in a vertical ridge-like shape along the transportation direction of the metal sheet 2. The metal sheet 2 above the ridge 4 a of the endmost disk cutter 4 is cut by the upper disk cutter 1 which is inward adjacent, to be formed as an end of the frame portion 2 g, and upward pressed by the ridge 4 a to the cutting plane S by 50% of the sheet thickness.

[0237] The metal sheet 2 in which the many slits 2 a are formed as described above is stretched toward both the sides in the width direction in the subsequent step of the rotary expander. As a result, as shown in FIG. 33, the slits 2 a are widened so as to form meshes, whereby a lattice-like grid is formed in which the nodes 2 c and the endmost nodes 2 f are connected to one another by four wires 2 b that are obliquely drawn out. In the same manner as Fig. 50, also in FIG. 33, twist of the node 2 c and the wire 2 b is omitted and the grid is diagrammatically shown.

[0238] According to the configuration, the vertical deformation of the endmost nodes 2 f in the metal sheet 2 is about a half of the sheet thickness. Therefore, concentration of stress in the endmost nodes 2 f is reduced. Even after the wire 2 b is obliquely pulled as a result of development, corrosion or heat generation hardly occurs in the endmost nodes 2 f, and there is little chance of breakage of the wire 2 b as compared with the usual node 2 c. Since the wire 2 b which is closest to the frame portions 2 g of the metal sheet 2 is hardly broken, it is possible to surely prevent the capacity of a lead storage battery from being largely reduced.

[0239] In the embodiment, the case where the outermost radius of the valley 1 b that is the endmost node forming valley is smaller than the predetermined radius by 50% of the thickness of the metal sheet 2 has been described. However, this difference is not restricted to 50% of the sheet thickness as far as the outermost radius is smaller than the predetermined radius. As the degree by which the outermost radius is reduced from the predetermined radius is smaller, the amount of the vertical deformation of the endmost nodes 2 f is larger. By contrast, when the degree by which the outermost radius is smaller than the predetermined radius is large, the vertical level difference with respect to the position where the metal sheet 2 is cut in the valleys 1 b other than the endmost node forming valleys becomes excessively large. When the outermost radius is smaller than the predetermined radius by 100% or more of the sheet thickness, the peripheral side face of the valley 1 b that is the endmost node forming valley cannot support the endmost node 2 f of the metal sheet 2. Therefore, it is preferable to set the outermost radius of the valley 1 b that is the endmost node forming valley, to be smaller than the predetermined radius by a degree in a range from 30% or more to 70% or less of the thickness of the metal sheet 2.

[0240] In the embodiment, the case where the peripheral side face of the ridge 4 a of the endmost disk cutter 4 is used as the reference circumferential face has been described. Alternatively, as shown in FIG. 34, the peripheral side face of the ridge 4 a may be formed as an inclined face similar to the outward inclined face 4 e of the valley 4 b other than the endmost node forming valleys. In the alternative, the peripheral side faces of the ridge 4 a of the endmost disk cutter 4 and the valley 4 b other than the endmost node forming valleys constitute the same inclined face, and the inward inclined face 4 d which is inclined in the opposite direction is formed only in the peripheral side face of the valley 4 b that is the endmost node forming valley.

[0241] In the embodiment, the case where the inward inclined face 4 d and the outward inclined face 4 e are formed in the peripheral side faces of the valleys 4 b of the endmost disk cutter 4 has been described. Alternatively, as shown in FIG. 35, each of the peripheral side faces of the valleys 4 b may be configured by a circumferential face. In FIG. 35, the peripheral side face of the valley 4 b (the left end in FIG. 35) that is the endmost node forming valley is configured by a circumferential face of a radius which is smaller than the predetermined radius by 100% of the sheet thickness, and the peripheral side face of the valley 4 b (the right end in FIG. 35) other than the endmost node forming valleys is the reference circumferential face of the predetermined radius. For example, the peripheral side face of the valley 4 b that is the endmost node forming valley may be configured by a circumferential face of a radius which is smaller than the predetermined radius of the reference circumferential face by 50% of the sheet thickness. In this case, the endmost node 2 f is abruptly changed in a small range as compared with the case where the inward inclined face 4 d is formed as in the embodiment. Although the amount of vertical deformation of the endmost node 2 f is identical, the node is abruptly changed in a smaller range in the axial direction of the disk cutter roll. In the embodiment, the groove 4 c is not formed in the endmost disk cutter 4. In the case where the groove 4 c is formed also in the endmost disk cutter 4 as in the prior art, the inner side of the peripheral side face of the valley 4 b stepwise sinks. Even when the peripheral side face is configured by a circumferential face of a radius which is smaller than the predetermined radius of the reference circumferential face by 50% of the sheet thickness, therefore, the endmost node 2 f is not abruptly deformed. Namely, the step due to the groove 4 c allows the metal sheet 2 to be gently deformed, in the same manner as the inward inclined face 4 d and the outward inclined face 4 e in the valleys 4 b in the embodiment.

[0242] As described above, the peripheral side face of the valley 4 b that is the endmost node forming valley in the endmost disk cutter 4 is requested only to have the outermost radius which is smaller than the predetermined radius, and not required to be a circumferential face. The peripheral side face may be a flat face which extends substantially along the circumferential face, a tapered face as in the embodiment, or a flat inclined face which extends substantially along the tapered face. Alternatively, the peripheral side face may have a step-like shape as in the case where the groove 4 c is formed, or may be an arbitrary curved face or a face of another kind. By contrast, in the valley 4 b other than the endmost node forming valleys, in order to cut the metal sheet 2 in combination with the valley 1 b of the upper disk cutter 1, at least the outer radius of the inner end must be larger than the predetermined radius and exceed the cutting plane S. As far as the conditions are satisfied, the valley 4 b other than the endmost node forming valleys may be configured by any kind of face.

[0243] In the embodiment, the case where the peripheral side face of the ridge 4 a of the endmost disk cutter 4 is the reference circumferential face of the predetermined radius has been described. Alternatively, as shown in FIG. 36, the peripheral side face of the ridge 4 a may be configured by a circumferential face of a radius which is smaller than the predetermined radius by 50% of the sheet thickness. In the alternative, the peripheral side face of the ridge 4 a has a radius which is equal to the outermost radius of the outer end of the inward inclined face 4 d of the valley 4 b that is the endmost node forming valley in the embodiment. Also the ridge 4 a must cut the metal sheet 2 in combination with the ridge 1 a of the upper disk cutter 1. Since the ridge 1 a of the upper disk cutter 1 downward protrudes in a ridge-like shape, the peripheral side face of the ridge 4 a of the lower disk cutter 1 can be formed as such a circumferential face of a radius which is smaller than the predetermined radius. However, the amount of the downward protrusion in both the basal areas of the ridge 1 a of the upper disk cutter 1 is small, and hence there arises the possibility that, in the areas, the radius of the peripheral side face of the ridge 4 a must be increased in order to cut the metal sheet 2.

[0244] In the embodiment, the case where the endmost disk cutters 4 are placed respectively at both the ends of the lower disk cutter roll has been described. Alternatively, one or both of the endmost disk cutters 4 may be placed in one or both ends of the upper disk cutter roll. Two or more paired disk cutter rolls may be used. For example, the metal sheet 2 can be passed through an arrangement of three disk cutter rolls.

[0245] In the embodiment, the case where the wires 2 b connected to the endmost nodes 2 f in the metal sheet 2, and those connected to the other nodes 2 c are formed so as to have the same thickness has been described. Alternatively, the wires 2 b connected to the endmost nodes 2 f may be formed so as to be particularly thicker, so that the wires 2 b are more hardly broken.

[0246] In the embodiment, the case where the metal sheet 2 is processed to produce a grid which is to be used in a battery plate of a lead storage battery has been described. The invention is not restricted to a lead storage battery, and can be applied also to a battery of any kind as far as a similar grid is used as a current collecting member of a battery plate. A grid can be produced by using a metal sheet of an appropriate material which corresponds to the kind of the battery.

EXAMPLE 5

[0247] By using rotary expanders in which the endmost disk cutters 4 of the embodiment, or the endmost disk cutter 4 of the prior art example are placed at the ends of the lower disk cutter roll, the slits 2 a were formed in the metal sheets 2, comparisons were then conducted. Results of the comparisons are shown in Table 5 TABLE 5 Breakage Ratio of rate of sheet endmost thickness node af- after ter cor- slitting Life per- rosion to origi- formance test Recess in nal sheet (prior (rate of valley Inclined thickness art = crack) (%) face (%) 100) (%) Remarks 0 None 60 100 42 Prior art example 10 None 69 103 35 Example 30 None 80 136 12 Example 50 None 90 152 0 Example 70 None 83 141 13 Example 100 None 63 110 37 Example 50 Formed 93 165 0 Example

[0248] As the metal sheet 2, a lead sheet of a thickness of 1.0 mm was used. The endmost disk cutters 4 configured in the following manner were used. In the prior art example, the peripheral side face of the valley 4 b coincides with the reference circumferential face of the predetermined radius (namely, in the prior art example, the valley 4 b is recessed by 0% of the thickness of the lead sheet 2). In the examples, the peripheral side face of the valley 4 b is configured by a circumferential face which is recessed from the reference circumferential face of the predetermined radius by 10% (0.1 mm), 30% (0.3 mm), 50% (0.5 mm), 70% (0.7 mm), or 100% (1.0 mm) of the thickness of the lead sheet 2. In the example, the outermost end of the peripheral side face of the valley 4 b is recessed by 50% of the thickness of the lead sheet 2, and the inward inclined face 4 d of 30° is formed in the peripheral side face. The interval distance between the upper and lower disk cutter rolls was fixed.

[0249] In each of the lead sheets 2 in which the slits 2 a were formed by the prior art example and the examples, after development to a grid, the thickness of the thinnest part in the endmost node 2 f was measured, and the ratio of the sheet thickness to the original thickness of the lead sheet 2 was calculated. An active material was filled into the grids, and the grids were then cured and dried to form positive plates. The plates were incorporated into lead storage batteries (Type 55D23 of JIS). An overcharge test according to JIS was conducted to test the life performance, and the breakage rate of the wires 2 b after the test was investigated. In all the lead storage batteries, a conventional plate was used as the negative plate, and a separator which is configured mainly by microporous polyethylene was interposed between the plates.

[0250] As a result of the comparison test, it has been confirmed that, in all of the grids produced by the examples, the sheet thickness ratio of the endmost node 2 f is larger than that of the prior art example, and elongation of the lead sheet 2 is suppressed. It has been confirmed also that life performance of lead storage batteries using the grids is improved and the breakage rate is reduced. Furthermore, it has been confirmed that the configuration in which the recess of the valley 4 b is in a range from 30% or more to 70% or less is particularly effective, with attaining the highest effect in the case where the recess is 50%. Moreover, it has been confirmed that the effect is further enhanced by forming the inward inclined face 4 d in the peripheral side face of the valley 4 b.

[0251] As apparent from the above description, according to the grid for a battery plate of the invention and the method of producing it, deformation of the endmost node of the metal sheet can be reduced by recessing the peripheral side face of the endmost node forming valley of the endmost disk cutter. Therefore, the wires drawn out from the endmost node can be surely prevented from being easily broken, a failure of a battery can be suppressed from occurring, and the life of a battery can be prolonged.

[0252] Preferred embodiments of the invention have been described.

[0253] In the following claims, for example, the invention can be implemented by combining any one of claims 2 to 5 with claim 6 or 7, or by combining any one of claims 2 to 5 with 13. Also when any one of claims 2 to 5 is combined with claim 18 or 19, or any one of claims 8 to 12, or with any one of claims 9 to 12, or when any one of claims 2 to 5 is combined with claim 15 or 16, it is possible to prevent rupture from occurring during a production process, to prevent corrosion and a crack of corrosion from occurring after production of a grid for a battery plate, thereby preventing the capacity of a lead storage battery from being reduced, and the life of the battery from being shortened. The invention can be implemented by combining claim 6 or 7 with claim 13, or by combining claim 18 or 19 with any one of claims 9 to 12. As described above, the claims of the invention relates to one another as a whole. These inventions belong to the same technique from the viewpoint that a crack of corrosion in a node of a grid which may occur during a process of producing a grid for a battery plate, or during use in a storage battery can be prevented from occurring so as to provide a storage battery of a long life. 

What is claimed is:
 1. A grid for a battery plate in which a large number of slits each configured by a out elongating in a longitudinal direction are formed in a metal sheet in a zigzag pattern, said metal sheet is stretched in a width direction to develop said slits, and nodes configured between slits that are adjacent in the longitudinal direction are connected to one another to form a lattice-like shape, by four wires which are configured between slits that are adjacent in the width direction, and which are obliquely bent to be drawn out, wherein at least one of said four wires connected to each of said nodes is bent in a predetermined oblique direction via a drawn-out portion which is drawn out from said node in a substantially longitudinal direction.
 2. A method of producing a grid for a battery plate in which a metal sheet is passed between two rotating disk cutter rolls in each of which a plurality of disk cutters are placed on a same shaft with forming a gap therebetween, each of said disk cutters being configured by: alternately forming ridges which protrude in a ridge-like shape toward an outer peripheral side, and valleys composed of a circumferential face or a flat face along a circumferential direction on a peripheral side face of a disk; and forming grooves which are opened in an outer peripheral end and in every other valley alternately formed in both faces of said disk, in peripheral edges of both said faces of said disk, said disk cutter rolls being opposed to each other in a manner that said ridges of said disk cutters of one of said disk cutter rolls are placed in said gaps of said disk cutters of another disk cutter roll, whereby slits each configured by a cut elongating in a longitudinal direction are formed in said metal sheet, wherein said valleys of said disk cutters of one of said disk cutter rolls which are placed respectively on both sides of said metal sheet are arranged with being shifted in phase from said valleys of said disk cutters of another disk cutter roll.
 3. A method of producing a grid for a battery plate in which a metal sheet is passed between two rotating disk cutter rolls in each of which a plurality of disk cutters are placed on a same shaft with forming a gap therebetween, each of said disk cutters being configured by: alternately forming ridges which protrude in a ridge-like shape toward an outer peripheral side, and valleys composed of a circumferential face or a flat face along a circumferential direction on a peripheral side face of a disk; and forming grooves which are opened in an outer peripheral end and in every other valley alternately formed in both faces of said disk, in peripheral edges of both said faces of said disk, said disk cutter rolls being opposed to each other in a manner that said ridges of said disk cutters of one of said disk cutter rolls are placed in said gaps of said disk cutters of another disk cutter roll, whereby slits each configured by a cut elongating in a longitudinal direction are formed in said metal sheet, wherein a length in a circumferential direction of said valleys of said disk cutters of said disk cutter roll which is placed on one side of said metal sheet is larger than a length of said valleys of said disk cutters of said disk cutter roll which is placed on another side of said metal sheet.
 4. A method of producing a grid for a battery plate in which a metal sheet is passed between two rotating disk cutter rolls in each of which a plurality of disk cutters are placed on a same shaft with forming a gap therebetween, each of said disk cutters being configured by: alternately forming ridges which protrude in a ridge-like shape toward an outer peripheral side, and valleys composed of a circumferential face or a flat face along a circumferential direction on a peripheral side face of a disk; and forming grooves which are opened in an outer peripheral end and in every other valley alternately formed in both faces of said disk, in peripheral edges of both said faces of said disk, said disk cutter rolls being opposed to each other in a manner that said ridges of said disk cutters of one of said disk cutter rolls are placed in said gaps of said disk cutters of another disk cutter roll, whereby slits each configured by a cut elongating in a longitudinal direction are formed in said metal sheet, wherein said grooves of said disk cutters of said disk cutter roll(s) which is placed on one side or both sides of said metal sheet are opened only in a part of a whole circumferential length of said valleys.
 5. A method of producing a grid for a battery plate in which a metal sheet is passed between two rotating disk cutter rolls in each of which a plurality of disk cutters are placed on a same shaft with forming a gap therebetween, each of said disk cutters being configured by: alternately forming ridges which protrude in a ridge-like shape toward an outer peripheral side, and valleys composed of a circumferential face or a flat face along a circumferential direction on a peripheral side face of a disk; and forming grooves which are opened in an outer peripheral end and in every other valley alternately formed in both faces of said disk, in peripheral edges of both said faces of said disk, said disk cutter rolls being opposed to each other in a manner that said ridges of said disk cutters of one of said disk cutter rolls are placed in said gaps of said disk cutters of another disk cutter roll, whereby slits each configured by a cut elongating in a longitudinal direction are formed in said metal sheet, wherein two or more of settings are made, said settings including: setting in which said valleys of said disk cutters of one of said disk cutter rolls which are placed on both sides of said metal sheet are arranged with being shifted in phase from said valleys of said disk cutters of another disk cutter roll; setting in which a length in a circumferential direction of said valleys of said disk cutters of said disk cutter roll which is placed on the one side of said metal sheet is larger than a length of said valleys of said disk cutters of said disk cutter roll which is placed on the other side of said metal sheet; and setting in which said grooves of said disk cutters of said disk cutter roll(s) which is placed on the one side or both the sides of said metal sheet are opened only in a part of a whole circumferential length of said valleys.
 6. A method of producing a grid for a battery plate wherein slits in which a small bent portion is formed between a node and a fence-like portion are formed in a metal sheet by using disk cutters of a rotary expander in each of which a plurality of ridges an apex of which is shifted toward a front side in a rotational direction protrude with forming a gap therebetween toward an outer circumference from a disk-like circumferential face at equal angular intervals, a small slope is interposed between a valley constituting a peripheral side face between two of said ridges, and at least a front slope of a peripheral side face of a ridge which is rearward adjacent to said valley, thereby connecting peripheral side faces, said small slope having an inclination angle which is between angles of said two faces, and grooves which are formed at equal angular intervals in peripheral edges of both disk-like faces are formed in every other gap face and opened alternately in both said faces.
 7. A method of producing a grid for a battery plate wherein slits in which a portion between a node and a fence-like portion is curved are formed in a metal sheet by using disk cutters of a rotary expander in each of which a plurality of ridges an apex of which is shifted toward a front side in a rotational direction protrude with forming a gap therebetween toward an outer circumference from a disk-like circumferential face at equal angular intervals, a curved face is interposed between a valley constituting a peripheral side face between two of said ridges, and at least a front slope of a peripheral side face of a ridge which is rearward adjacent to said valley, thereby connecting peripheral side faces, said curved face having a contact face of an inclination angle which is between angles of said two faces, and grooves which are formed at equal angular intervals in peripheral edges of both disk-like faces are formed in every other gap face and opened alternately in both said faces.
 8. A method of producing a grid for a battery plate wherein slits in which a node is inclined are formed in a metal sheet by using disk cutters of a rotary expander in each of which a plurality of ridges an apex of which is shifted toward a front side in a rotational direction protrude with forming a gap therebetween toward an outer circumference from a disk-like circumferential face at equal angular intervals, a valley constituting a peripheral side face between two of said ridges is formed into a face which is more inclined toward a center as being more forward than a contact face contacting with a circumferential face in which all contacting faces contacting with said valley have a same angular position at a center of a rotation shaft, and grooves which are formed at equal angular intervals in peripheral edges of both disk-like faces are formed in every other gap face and opened alternately in both said faces.
 9. A method of producing a grid for a battery plate in which a plate is produced by a rotary expander for forming slits in a metal sheet by using disk cutters in each of which a plurality of ridges an apex of which is shifted toward a front side in a rotational direction protrude with forming a gap therebetween toward an outer circumference from a disk-like circumferential face at equal angular intervals, and grooves which are formed at equal angular intervals in peripheral edges of both disk-like faces are formed in every other valley constituting a peripheral side face between said ridges, and opened alternately in both said faces, wherein each of said valleys of said disk cutter is formed into a face which is more inclined toward a center as being more forward than a contact face contacting with a circumferential face in which all contacting faces contacting with said valley have a same angular position at a center of a rotation shaft of said disk cutter.
 10. A method of producing a grid for a battery plate according to claim 8 or 9, wherein said valley is formed into a face which is more inclined by 1° or more toward the center as being more forward than said contact face contacting with said circumferential face in which all contacting faces contacting with said valley have a same angular position at the center of said rotation shaft of said disk cutter.
 11. A method of producing a grid for a battery plate according to any one of claims 8 to 10, wherein only a face of said valley excluding a front end portion is formed into a face which is more inclined toward the center as being more forward than said contact face contacting with said circumferential face in which all contacting faces contacting with said valley have a same angular position at the center of said rotation shaft of said disk cutter.
 12. A method of producing a grid for a battery plate according to any one of claims 8 to 11, wherein the circumferential face serving as a reference of inclination of said valley is a flat face connecting together cross lines between said circumferential face and said slopes of said ridges on both the sides.
 13. A method of producing a grid for a battery plate in which a rotary expander is used for forming a large number of zigzag slits in a metal sheet by passing said metal sheet between two or more opposed disk cutter rolls, each of said disk cutter rolls being configured by placing a plurality of disk cutters on a same shaft with forming a gap therebetween, each of said disk cutters being configured by: alternately forming ridges in which a peripheral side face protrudes in a ridge-like shape toward an outer periphery from a reference circumferential face of a predetermined radius, and valleys in which a peripheral side face composed of a face substantially extending along the said circumferential face is formed, in a whole periphery of a peripheral edge of a disk, said reference circumferential face being centered at an axis of said disk; and, for each of said valleys, forming a groove which is opened in a peripheral side face of said valley, in a peripheral edge portion of one of disk faces in which valleys that are adjacent to each other via a ridge are formed in an oppositely reverse manner, wherein in each of said disk cutters, an inclined face is formed in peripheral side faces which extend from apexes of ridges formed on both sides of each of said valleys to said valley, said inclined face more approaching the axis as being nearer to said disk face in which said groove of said valley is formed.
 14. A grid for a battery plate which is produced by the production method of claim
 13. 15. A method of producing a grid for a battery plate in which a plurality of parallel slits are cut in a metal sheet into a zigzag pattern along an advancing direction of the metal sheet, wires which are formed by slits that are adjacent in a width direction of said metal sheet are elastically deformed in a ridge-like shape in both front and back directions from a face of said metal sheet, flat regions which are formed by non-slit portions are formed to become nodes of said wires, and said metal sheet is developed in the width direction, thereby forming meshes, wherein said slits which are cut into a zigzag pattern are formed by passing said metal sheet through a roll pair in which rolls are opposed to each other, each of said rolls is configured by stacking disk cutters each having ridges and valleys, said ridges protruding at regular intervals from a circumference of said disk cutter, and, in said disk cutter, grooves are disposed in a thickness direction in each of said valleys between said ridges and alternately in both disk faces corresponding to said nodes, and chamfered portions are disposed in an outer peripheral portion of a peripheral side face of said disk cutter, said outer peripheral portion excluding at least said ridges, said chamfered portions being lowered as being respectively nearer to said faces in which said grooves are disposed.
 16. A method of producing a grid for a battery plate according to claim 15, wherein said chamfered portions between said peripheral side face of said disk cutter and said disk faces of said disk cutter in which said grooves are formed are planer or curved chamfered portions.
 17. A battery comprising a grid for a battery plate which is produced by the method of claim 15 or
 16. 18. A method of producing a grid for a battery plate in which a rotary expander is used for forming a large number of zigzag slits in a metal sheet by passing said metal sheet between two or more opposed disk cutter rolls, each of said disk cutter rolls being configured by placing a plurality of disk cutters on a same shaft with forming a gap therebetween, each of said disk cutters being configured by: alternately forming ridges in which a peripheral side face protrudes in a ridge-like shape toward an outer periphery from a reference circumferential face of a predetermined radius, and valleys in which a peripheral side face composed of a face substantially extending along the reference circumferential face is formed, in a whole periphery of a peripheral edge of a disk, the reference circumferential face being centered at a rotation axis of said disk; and, for each of said valleys, forming a groove which is opened in a peripheral side face of said valley, in a peripheral edge portion of one of disk faces in which valleys that are adjacent to each other via a ridge are formed in an oppositely reverse manner, wherein among said disk cutter rolls, a disk cutter roll which is opposed to a disk cutter roll having a disk cutter that is disposed outermost is provided with a disk-like endmost disk cutter that is placed more outward than said outermost disk cutter, and a peripheral side face which is recessed toward a center with respect to said reference circumferential face is formed in a valley (hereinafter, referred to as “endmost node forming valley”) which corresponds to a valley in a disk cutter of another disk cutter roll that is opposed via said metal sheet, among valleys of said endmost disk cutter (in said endmost disk cutter, peripheral edge portions respectively corresponding to valleys of another disk cutter of a same disk cutter roll are referred to as “valleys”), a groove being formed in a disk face in said groove of said disk cutter of said other disk cutter roll, said disk face directed to said endmost disk cutter.
 19. A method of producing a grid for a battery plate according to claim 18, wherein an inclined face is formed in said peripheral side face of said endmost node forming valley, said inclined face being nearer to the center as being more inward.
 20. A grid for a battery plate which is produced by the production method of claim 18 or
 19. 